The book(s) you want to get are in the 'original' series. There are two versions of 'Original Jaguar XK'. Both by Philip Porter. One just a newer edition of the other, and the earlier out of print I think. Get both. Shouldn't be hard to find on ebay.
*Edit*... looks like there are three editions perhaps of that... the first two in hardbound are the ones I've got... time to go shopping again.
*End edit*
Also find a copy of the 'Jaguar Enthusiast Club on Jaguar XK 120 Restoration'. Mostly a compilation of articles from the club magazine, but very informative, and most things would be applicable to a XK140.
And get a copy (or original) of the original service and parts manuals.
You get all them, and you'll be set bookwise. All turn up regularly on ebay.
To definitavely get the color, get the JDHT (Jaguar Daimler Heritage Trust) certificate for your car. It can be hard to find the original color if the car has been restored or properly re-sprayed in its life. You'd have to look for overspray in very hidden areas.
You're in for a lot of fun... Enjoy!
-Matt
'53 120 FHC