Hi, Lee.
I'm not sure if these are the 'best' paints for greys and reds, but I use mostly
Wargames Foundry paints. The actual colors of the coats could vary wildly depending on many factors so most shades would be fine.
I normally paint in triads (three layers - not sure how familiar you are with painting minis) For Greys I've used...
Slate Grey (32A-C)
Slate Grey (32C) and Arctic White (33A and B)
Stone (57A-C)
British Gun Grey (108A-C)
For Reds...
Bright Red (15A-C)
Terracotta (37A-C)
British Redcoat (68A-C)
I find Foundry gives pretty good coverage with a single coat of the 'A' color with maybe a quick touch up here and there. I think there are some Games Workshop paints mixed in as well, but I don't recall the actual colors. The
GW Base paints are amazing for smooth colors in one coat, even painting yellow over black for instance.
You can find all of my units in the
1690 page of my blog. If you hunt around
older posts with the BLB tag on the blog, some of them have the specific paints I used. I think there are some Games Workshop paints mixed in as well, but I don't recall the actual colors...
This post from the
LoA blog is also worth a quick read.
Hope that helps!