Photos that look ok, often give dull results if seen through a kaleidoscope. Seeing the abstract symmetrical image, I expect more vivid colors. Thus I searched for a way to increase the color saturation to a maximum. Using the hue-saturation-brightness mode for color in processing I found a simple solution.
For each pixel I use processings functions to get its hue, saturation and brightness. Then I put the saturation to its maximum value and calculate this new color for the pixel. This works well except for grey or white colors, which give terrible spotty images as their hue is not well-defined. Thus I only put the saturation equal to the maximum value if it exceeds a threshold value. The saturation decreases linearly to zero below the threshold value.
The results resemble old black and white picture cards that have been colored by hand: