Generate distinctly different RGB colors in graphs

Question

When generating graphs and showing different sets of data it usually a good idea to difference the sets by color. So one line is red and the next is green and so on. The pro

Answer 1

I needed the same functionality, in a simple form.

What I needed was to generate as unique as possible colors from an an increasing index value.

Here is the code, in C# (Any other language implementation should be very similar)

The mechanism is very simple

1. A pattern of color_writers get generated from indexA values from 0 to 7.

2. For indices < 8, those colors are = color_writer[indexA] * 255.

3. For indices between 8 and 15, those colors are = color_writer[indexA] * 255 + (color_writer[indexA+1]) * 127

4. For indices between 16 and 23, those colors are = color_writer[indexA] * 255 + (color_writer[indexA+1]) * 127 + (color_writer[indexA+2]) * 63

And so on:

    private System.Drawing.Color GetRandColor(int index)
    {
        byte red = 0;
        byte green = 0;
        byte blue = 0;

        for (int t = 0; t <= index / 8; t++)
        {
            int index_a = (index+t) % 8;
            int index_b = index_a / 2;

            //Color writers, take on values of 0 and 1
            int color_red = index_a % 2;
            int color_blue = index_b % 2;
            int color_green = ((index_b + 1) % 3) % 2;

            int add = 255 / (t + 1);

            red = (byte)(red+color_red * add);
            green = (byte)(green + color_green * add);
            blue = (byte)(blue + color_blue * add);
        }

        Color color = Color.FromArgb(red, green, blue);
        return color;
    }

Note: To avoid generating bright and hard to see colors (in this example: yellow on white background) you can modify it with a recursive loop:

    int skip_index = 0;
    private System.Drawing.Color GetRandColor(int index)
    {
        index += skip_index;
        byte red = 0;
        byte green = 0;
        byte blue = 0;

        for (int t = 0; t <= index / 8; t++)
        {
            int index_a = (index+t) % 8;
            int index_b = index_a / 2;

            //Color writers, take on values of 0 and 1
            int color_red = index_a % 2;
            int color_blue = index_b % 2;
            int color_green = ((index_b + 1) % 3) % 2;

            int add = 255 / (t + 1);

            red = (byte)(red + color_red * add);
            green = (byte)(green + color_green * add);
            blue = (byte)(blue + color_blue * add);
        }

        if(red > 200 && green > 200)
        {
            skip_index++;
            return GetRandColor(index);
        }

        Color color = Color.FromArgb(red, green, blue);
        return color;
    }