When designing logos or icons I like to work in black and white or grayscale for the initial design so I don’t get distracted by the colors, and then color it last. Illustrator’s “recolor artwork” feature is a great tool for experimenting with colors, but by default it won’t recolor black and white artwork.
To recolor black and white artwork you have to click on the color reduction options icon and uncheck the Preserve option for Black, White and/or Grays.
This may be obvious to those who use Illustrator a lot, but I don’t and this really had me pulling out my hair, which I really can’t afford to do!!