I have to rescreen the basement window screen and the front sliding
glass door screen.

I want to use vinyl, but does it matter if I use grey, black, or any
color if there is any?

Does it matter if most people looking through the screen will be
looking out of the house or into it? Does it matter if the door is on
the north side of the house, or on the sunny south side?

IIRC, black can be less noticeable than grey, but it seems to me that
would depend on the things above, looking out or in, if it is sunny
out or not.

I already have the screening in black**, but I expect this to last at
least another 25 years, so it would be worth buying the other color if
it matters.

**I'm sure I bought it but I don't remember why, since the screen door
has only been ruined for about a year, and I bought it years before
then. (Unless someone gave it to me. ??)