Make the blob nucleus more visible

[TheNewTeddy]

I invented a new fun internet game, it's called 'find that nucleus'



need a hint?
I tried to highlight it using MS Paint, figuring I could click on the circle sprite with another colour (red) and it would show.
However; this happened instead.

Spoiler!

Literally invisible. Pixels are not even different colours.
.

I strongly but humbly suggest black be removed as a colour until this can be sorted out, ASAP, IMHO.