How to draw a color wheel in illustrator?

Question

How to draw a color wheel in illustrator? I am thinking of creating many small arcs with gradient and all hue colors. Any ideas?

Answer 1

One way would be to apply a linear gradient on the stroke. Create a circle, and stroke it with a gradient pattern. Make sure the gradient has the stops like in the table and picture below. The gradient might not look as smooth in the transitions, but that's all that comes to mind.

+------------+---------------+----------+
| Color Stop |      RGB      | Location |
|------------+---------------+----------|
|      1     | (255, 0, 255) |    0.00% |
|      2     | (0, 0, 255)   |   16.67% |
|      3     | (0, 255, 255) |   33.33% |
|      4     | (0, 255, 0)   |   50.00% |
|      5     | (255, 255, 0) |   66.65% |
|      6     | (255, 0, 0)   |   83.33% |
|      7     | (255, 0, 255) |  100.00% |
+---------------------------------------+

Answer 2

I don't have Illustrator, but this is the general technique I can do in GIMP. The same technique should be applicable to Illustrator:

1. Start with black background
2. In gradient editor, create a custom gradient that consists of three equal-sized segments. The first third is solid foreground color, the second third is linear gradient from foreground to background color, and the last third is solid background color (see Appendix below for what it should look like).
3. Select Gradient Tool
4. Select Conical (Symmetric) gradient
5. Select Addition blending mode
6. Draw three gradients, in three directions (0deg, 120deg, 240deg), with three different foreground colors (e.g. #ff0000, #00ff00, #0000ff) to black background color.

Result

Alternatively, when you inverse all the colors and gradients, and then use Multiply blending mode, you would get the exact same result as what you would get with Addition:

1. Start with white background
2. Create a gradient just like in the Addition mode, but swap the foreground and background color. Create a custom gradient that consists of three equal-sized segments. The first third is solid background color, the second third is linear gradient from background to foreground color, and the last third is solid background color (see Appendix 2 below for what it should look like).
3. Select Gradient Tool
4. Select Conical (Symmetric) gradient
5. Select Multiply blending mode
6. Draw three gradients, in three directions (0deg, 120deg, 240deg), with three different inverse foreground colors (e.g. #00ffff, #ff00ff, #ffff00) to white background color.

Result

Why does this work?

If you use the color picker around the color wheel, one thing you'll notice is how the RGB color changes as you move your picker around the color wheel. First you start with pure red (#ff0000), then as you rotate, you'll notice how green linearly increases until you get yellow (#ffff00), then you rotate further and red linearly decreases until you get pure green (#00ff00). From here the same thing happen with green and blue, blue linearly increases until cyan (#00ffff), followed by green linearly decreasing until you're left with pure blue (#0000ff). And then again with blue and red, red linearly increases until magenta (#ff00ff), followed by blue linearly decreasing until we wrap back around at pure red (#ff0000).

Essentially, what we are creating with our conical gradient is adding the primary colors (Red, Green, Blue) onto a black (#000000) background:

The "addition" blending mode mathematically adds the colors to the layer below it (or in case of gradient tool, to the existing image). This means that if the layer below it has the color #112233 and the color you want to "Add" is #010203, the new color would be #112233 + #010203 = #122436.

Adding the three conical gradients together into a black background, we get the color wheel that we expected.

While the Addition technique works by adding colors to the black (#000000) canvas, like making a clay statue. The Multiply technique works by essentially carving out unwanted colors (the inverse colors) from white (#ffffff), like a sculptor. They both produces the exact same result through very different ways.

Appendix

This is what the gradient editor should look like in Addition technique:

Appendix 2

This is what the gradient editor should look like in Inverse and Multiply technique: