Your local FSDO should be able to answer any questions like this. There is a PDF on faa.gov that lists both telephone numbers and appropriate email accounts for each FSDO.
and no, painting is not a major modification. On a RV-10, that would be changing the prop or engine, or deciding that you want to use RV-7 wings instead.
Well, no, not really. What is acceptable to one FSDO may not be acceptable to another, which runs the risk of causing problems down the line and while trying to please the FAA or CAsA is always a good idea, education "sometimes" works too.
The actual rule is 14 CFR 21.93 (a) that says "In addition to changes in type design specified in paragraph (b) of this section, changes in type design are classified as minor and major. A “minor change” is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product.All other changes are “major changes” (except as provided in paragraph (b) of this section)."
From their own AC, if it is likely to have a significant effect on:
Weight
Balance
Structural Strength
Performance
Powerplant operation
Flight characteristics
Other qualities affecting airworthiness
Then it is deemed to be a major mod that requires data. They even have flowcharts to help you out with the process: