John Sukey (who does know his onions from his apples) posted this in another thread:
"Paint;
"Green; fully serviceable
"Yellow; Serviceable, but not as good as green
"Red; don't let a live round anywhere near it!
"White; strictly for square bashing (drill rifle)
"All cadet markings"
That said, there were any number of REASONS for the paint in the first place. NOT all Drill rifles were junkers. Many needed only very minor work, sometimes none at all, to be good shooters.
Sometimes, if they had a need for rifles for Drill Purposes, they would just take a bunch from th READY rack and mark them as DPs. They were still SAFE but were maintained at a lower level.
I have a Lithgow 1918 SMLE with bright RED paint on it; all it needed was The Damned Crack repaired; otherwise it was a new rifle. It shoots well under 1 MOA.
BEST thing to do is to have someone who is familiar with Lee-Enfield rifles look it over carefully.
It IS a beautiful rifle.