Normal is right.  Cats' skin differ one from the other.  I have a totally
black cat with skin as white as a post-bleach Michael Jackson.  One of my
black and gray tabby cat's skin exactly matches the stripes in her coat.

I have a calico with black splotches in her gums and upper mouth that mimic
the same as her outsides.

--Geno

Hi,

If a cat has ringworm then you will see a darker circular spot under
their fur at the roots and in a black cat the fur in that area may
even be lighter in colour. If you get an ultraviolet light and shine
it on the area in a dark room then you will see a greenish tinge to
it. You'll also see a lot of green looking dust in their coats but you
don't need to bother about that.

You can get a special shampoo from a vet or pet shop to treat ringworm
with a 'few' washes or directly rubbing the shampoo (then rinsing off)
on the affected area for a few weeks.

We have a black and white cat and underneath she is patchy skin
coloured too. Looks nice actually.

Iain Halder