Minecraft wiki entry for Procedural_animated_texture_generation, associated text: Calculates a color_heat as the soup_heat clamped between 0 and 1 inclusive.
Then it calculates the color components of the pixel as follows:
float red = 32 + color_heat^2 * 32
float green = 50 + color_heat^2 * 64
float blue = 255
float alpha = 146 + color_heat^2 * 50