There is a cool, albeit thin, book entitled Amps by Richie Fliegler (ISBN 0793524113) that was published by Hal Leonard. It gives a good, brief explanation of how tube amps work. It also gives a brief history of how various companies came into being and addresses some specific models. Brands like: Marshall, Park, Fender, Gibson, Vox, Ampeg, Sunn, Mesa Boogie, Soldano, Matchless, Gretsch, Rivera, Orange, Custom, etc. It has lots of pictures that will give you a big, rubbery one. There is also a chapter on vintage vs. re-issue.
Page 93 features a picture of two, vintage, purple Marshall half stacks. Personally, I think the twilight color of the vintage modern is cooler. I also think the twilight color emphasizes the something old, something new character of the vintage modern.
Check it out.