Bob Keen wrote:...I hope that it remains free...
I've had a free MyHeritage account for several years. It allows you to do unlimited searches of their genealogy records but it is very limited in what you can see beyond the index list returned by a query. To that detail you do need a subscription. [Or you use the list of hits to inform further searching at a library where you can get full access Ancestry for free]
I don't know if the number of photos you can colourise with a free account is limited. I've only tried a couple so far, the test one of the butterfly (which was only taken a few ago so I have a full colour version), and one from the 1920s of two young American sailors in their dress uniforms. It left the 'summer' uniform white and applied a sensible navy blue to the 'winter' one. The flesh tones were OK too. Having said that, it took me two attempts. The first time I uploaded the image 'as is', with a faint sepia hint to it. It simply 'improved' the sepia effect. Second time I upload a true B&W version (which I made using Affinity Photo 2). It applied colour to that version.
Affinity Photo user with a Canon camera