[In SA it's Prestik (Bostik) - I've never seen Blu-tac.] I think you won't get black. You could try coloring it with black permanent marker, or sticking a tiny piece of masking tape over it and colouring that. (If it's not the tiny pinhead-size LEDs.)I use Blue Tack to mask annoying LEDs on the fronts of components. I'd really like to get it in black, but I'm having trouble shopping for it because "Blue Tack" is a brand name and it's not obvious what the generic name for it is. I've managed to find some in white but not yet black. Any advice anyone please?
Google not showing any generic name, just "...original rubber based reusable putty adhesive"