Coloring a binary mask image

ImageMultiply[im, Green] // AbsoluteTiming

enter image description here

versus 0.031786 for colorizeMask4 (fastest of the five in OP).

Alternatively, ColorCombine the mask with an all-black image:

im = Binarize[RegionImage[Annulus[], RasterSize -> 1024]];
black = ImageMultiply[im, 0];
ColorCombine[{black, im, black}] // AbsoluteTiming

this takes 0.001806 vs 0.019607 for colorizeMask4

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