Yes, it's true. I volunteered at our local animal shelter for 14 months in the, what was then called "Cat-Nip" program, helping potential adopters find their forever friend. Black cats and even dogs do not get adopted as much. At Halloween time the shelter intentionally will NOT adopt out a black cat, for fear of someone adopting one and intentionally harming it for superstitious & Halloween related stuff. It's sad but true.
We will likely adopt two at the same time. If they're related that would be great, but not absolutely necessary. If possible I think one should be black.
"Opportunity is missed by most people because it is dressed in overalls & looks like work" - Thomas Edison