I would suggest just going with RCA volume 1. It shows about 20 different Berks rifles, with multiple views of each rifle plus the measurements. True, it's only in B&W, but for studying the rifles it's still the best.
Berks County Longrifles and Gunmakers shows some nice rifles, but in the book I received, the color printing is very dark and makes the details difficult to see. I don't know if all were printed that dark, but the copy I have certainly is. If you purchase that book, I'd suggest having the book in hand, and look through it before you purchase.
John