Commercial paint suppliers (such as PPG etc), such as service auto paint shops, should have a $20k color scanner they can bring to the airplane to determine paint codes, ALMOST perfectly.
For parts that can come off, you can bring to a good local auto paint shop.
You can also buy nice inexpensive airbrushes with compressors etc.
Balancing controls another question.
I would think the design counterweights should keep everything quite stable, unless you slop it on. The following demonstrates
https://youtu.be/xJTtp_8_z6c