Removing magic numbers from color generator

[TornaxO7]

I'd like to change the constant numbers with constant variable names to make it easier to understand those constant numbers in the color generator. But I don't fully understand what your calculations are doing here:

• https://github.com/zesterer/ariadne/blob/main/src/draw.rs#L149
• https://github.com/zesterer/ariadne/blob/main/src/draw.rs#L152
• https://github.com/zesterer/ariadne/blob/main/src/draw.rs#L153
• https://github.com/zesterer/ariadne/blob/main/src/draw.rs#L154

Could you please explain them a bit and do you agree to move those constants to variables/(named) constants?