Japanese hooded rat

Good suggestion.

Albino

I've always been partial to brown.

Dominus tecum

Sent some interesting options in private messages

White with a brown “saddle” and a brown eye patch.

As someone who has had pet rats for years, i'd recommend looking up Fancy Rat colorings.
Personal favs have been black stripe on back with white belly, or white with golden brown markings on back.

White, that way you can run around in a lab coat.

Husky rats are pretty cool: https://www.flickr.com/photos/3hanhs/8087451139

The markings get lighter as they age.

Oo that looks cool. I love hooded rats also.

I second that suggestion

I'm partial to the plain gray Rattus Norwegicus, but I'm biased from the Herman Orca stories.

Charles Matthias? That rat's got character and you're quite familiar with him.

Also... a hooded rat would be interesting. Or a Spuds McKenzie rat...

How about the black-and-white Husky Rat?

I am perhaps strange - while likely not existing in reality or nature, a rat with the same smoky near-blue color you see in come cats would be very handsome, as would one of particularly nigh-impossible colors, like the glossy, high-sheen turquoise blue-green coat seen on some Warframe Kavats.

I'm partial to black hooded rats, my family does Archery, and my grandmother was a rat in the Chinese zodiac

Black hooded Archer with some asian influences thrown in?

Those are great suggestions and I did go with a black hooded rat. But too late for the rest. I’ve got the sketch all done.

Hooded rats cutest rats. o.o