I wrote the two methods below to automatically select N distinct colors. It works by defining a piecewise linear function on the RGB cube. The benefit of this is you can also get a progressive scale if that’s what you want, but when N gets large the colors can start to look similar. I can also imagine evenly subdividing the RGB cube into a lattice and then drawing points. Does anyone know any other methods? I’m ruling out defining a list and then just cycling through it. I should also say I don’t generally care if they clash or don’t look nice, they just have to be visually distinct.
public static List<Color> pick(int num) { List<Color> colors = new ArrayList<Color>(); if (num < 2) return colors; float dx = 1.0f / (float) (num - 1); for (int i = 0; i < num; i++) { colors.add(get(i * dx)); } return colors; } public static Color get(float x) { float r = 0.0f; float g = 0.0f; float b = 1.0f; if (x >= 0.0f && x < 0.2f) { x = x / 0.2f; r = 0.0f; g = x; b = 1.0f; } else if (x >= 0.2f && x < 0.4f) { x = (x - 0.2f) / 0.2f; r = 0.0f; g = 1.0f; b = 1.0f - x; } else if (x >= 0.4f && x < 0.6f) { x = (x - 0.4f) / 0.2f; r = x; g = 1.0f; b = 0.0f; } else if (x >= 0.6f && x < 0.8f) { x = (x - 0.6f) / 0.2f; r = 1.0f; g = 1.0f - x; b = 0.0f; } else if (x >= 0.8f && x <= 1.0f) { x = (x - 0.8f) / 0.2f; r = 1.0f; g = 0.0f; b = x; } return new Color(r, g, b); }
You can use the HSL color model to create your colors.
If all you want is differing hues (likely), and slight variations on lightness or saturation, you can distribute the hues like so: