Color theory (level design)
General Color Theory
First a bit on color theory in a general practice: Wikipedia (look below) tells us the color wheel is set up to show 12 important colors. 3 are primary, 3 are secondary (mixing the primary colors) and 6 tertiary colors (created by mixing primary and secondary colors). Your primary colors form a triangle, (Yellow, Blue and Red). The secondary colors (Green, Purple and Orange are directly in between the primary colors). These also form an upside down triangle. The tertiary colors are in between the primary and secondary colors and will provide your shades of colors. This is important because of how people perceive color combinations.
Color Perception
Colors found next to each other blend well, colors directly across contrast each other, and colors 1/3 the way round help accent. This means if you were to use yellow then the colors yellowy-green, pale orange, blue, red, and purple can all work with it if used properly. The key comes from the fact that if you choose yellowy-green to work with yellow then blue becomes a tricky color to use as blue doesn't work cleanley with yellowy-green.
The colors you pick define everything about an image. What the viewer feels, where they look, what belongs there, and what they notice the most because they saw it first or last.
This is a solid example of using complimentary colors to work to a nice visualy appealing goal. The colors work together and you can see each color fitting in with the rest. The things your attention is drawn to are the focus of the image such as the name, slogan, and properties.
This is another approach to the same bottle, the color palette in its entirety has been shifted, no individual color changed on its own, all colors changed the same amount. It all still fits together proving that an established palette is the key to a solid image.
This personifies what not to do, colors taken randomly from everywhere thrown together to make a mess of what can be a good image. Your eyes focus on the wrong things, some properties fade into the background while the sub title becomes more noticeable than the name.
The first images were easy to look at but the last image was one that did not feel right at all. Taking the colors used as more than colors helps your image feel better to the viewer.
Effect of Color
A color does more than simply define how objects look. Sight is the primary human sense, whatever we see affects us deepley and carries more effect than just that of an image. Each color has feelings and meanings attached to it. Take red for example.
A color of passion, of romance, of danger, of warmth, of blood.
When asked to list what red means or feels this is a pretty standard list. What shade you pick and how you use it the image can give any feeling or any meaning, but thiers preconceptions to deal with like the ones above. Everyone knows a red light means stop, green means working, blinking means busy. When creating a scene if you ignore how each color is used in life people will misinterpret what their supposed to see and feel. Every color has an inbuilt meaning and using that meaning is what allows you to create an atmosphere in level design. For example in Half Life 2 pale blue lights to create a cold feeling in the combine citadel. Warm yellow lights to create a comfortable feeling inside the teleporter labs. Half Life 2 uses this as a practice and you can aswell.
It starts by picking the mood of the area. The mood you wish to achieve should affect what textures you pick and what lighting colors you use. For example lets pick a creepy swamp. Black is a very mysterious and threatening color so we'll go with darker shades and low brightness values. You expect greens for algae and swampy water as this is a swamp we'll include those into the palette. But we need a hut for this, so go back up to the color wheel. Orange is 1/3 round from green and a dark shade gives us brown. This gives a perfect accent color so we'll go for a wooden hut to use it. Now you have key colors, materials and a feeling, by sticking to textures and light that work with the theory of your key colors and moods the scene will make itself. The only thing missing is a point of focus.
Point of Focus
The point of focus is simply what you want the player to be looking at. Wheter its a distraction, the piece of a puzzle, the way out, or even the next enemy its where the player should be looking and going. While creating a true point of focus may be beyond this atricle it can be done by any means including sound, motion, shape, light or color. As this is a color theory article I shall only involve light and color. The simplest way to do it with color and light is accents and contrasts a bright light in a dark room, a blue traffic cone in a line of red ones. As stated before these can work well in a scene so its often not hard to include a point of focus. The key becomes making it the right object at the right time.
If we go back to our example of the swamp and our hut we'll work the hut as the point of focus. As the palette will be mostly dark greens and browns the best way to make the hut stand out is to use light. Add a light to the hut and it becomes almost instantly a perfect point of focus, an accented color under conrasting brightness. The player will notice the hut and move towards it. Because it's noticable, it stands out.
But lets flip the coin to the other side, and move to a red brick alleyway. Brick buildings lining both sides, you include an area on the roofs thats out of reach its just where enemies come from. You throw in a green dumpster and move on. Red and green, contrasting colors, they fit in the scene. You playtest the game and here comes the problem. You know the player can't get up there, but the player will notice the dumpster as it's a contrast element. You find the player tries jumping around on the dumpster for 5 minutes because he thinks thats how he's supposed to get to the roof. He hasn't noticed the door because its only an accent color.
This is the problem with point of focus in color and light. You can make the wrong area seem important if you don't watch how your scene comes together.
An Example
Here I'll talk about a screenshot from HL2. The base palette for the level begins at the walls the cream, dusty red and burgenday set up a solid color range with nice accents and the burgendy as a slight contrast. The burgendy and cream gets carried into the floor tiles and rust in the railings creating strong visually appealing floors and railing that fit in. the ceilngs blend in niceley going for the more cream approach. the antlions being very earthy browns and oranges blend into the scene easily as they blend well with the colors of the walls and floors.
The Combine and the concrete however form a very blue palette between their uniforms and the pale blue grey found in the floors and some ceilings. This also continues into the barrels. So we have 2 palletes, usually that is a poor approach but lets roll back to the color wheel and look where the palletes place. Oranges and red sit opposite and 1/3 of the way round from the blue, because of this fact they appear to accent and contrast thus sitting together niceley in the same image. Shifting the blue colors to a military green and an outdoor grass would create a green pallete, while this lines up at 1/3 on the color wheel the result would not be as appealing as it does not match on as many levels.
The darker approach to the image give the unneasy feeling, the poitns of brightness fade out into the darker parts of the pallete giving that cold feeling. The warmer colors of the burgedy cream and yellow lights get lost and isolated in the grey compounding the feeling of being isolated more than breaking it up. Contrasting emotions of colors rather than just colors themselves.
In the image your first focus is the combine, thier blue contrasts the main pallete forcing you to notice them, as you follow the combine you notice the antlions as they blend in with the walls and ground but don't match it. Following the walls you explore the scene catching the bright light above for a few moments. Eventually your eyes come to rest on the barrels as they stand out the most using a shade of blue that doesn't fit in with the rest of the image as well as everything else does.