At first, I'd follow the guideline in the Gunpla manual to buy all the mentioned color. After a few round of modeling test, I concluded that other than the exception case i.e. the color of MG Infinite Justice, I'll only need the following color for most of my color application.
Mr Color List
1. White
2. Character White
3. Cobalt Blue
4. Red Madder
5. Character Yellow
6. Neutral Grey
7. Midnight Blue
8. Navy Blue
9. Bright Green
10. Fluorescent Pink
11. Fluorescent Yellow
12. Fluorescent Orange
13. Fluorescent Green
14. Super Clear Semi Gloss
15. Clear Yellow
16. Clear Orange
17. Clear Blue
18. Clear Green
19. Steel
And here's some example on how I'd mix my Gundam Color.
1. Blue
Cobalt Blue + little bit of fluorescent pink + white (if needed)
2. Red
Red Madder + little bit of fluorescent orange + white (if needed)
3. Yellow
Character Yellow + white + little bit of fluorescent yellow
4. Frame Color
Steel
5. Gray Color
Neutral grey + Midnight Blue/Navy Blue (Prefer Midnight Blue most of the time)
6. Dark Blue
Cobalt Blue + Midnight Blue/Navy Blue (Prefer Midnight Blue most of the time)
7. Dark Red
Red Madder + Midnight Blue/Navy Blue (prefer Midnight Blue most of the time)
8. Dark Yellow
Character Yellow + Midnight Blue/Navy Blue (prefer Midnight Blue most of the time)
9. Black
Midnight Blue
10. Camera Eyes
Clear + little bit of Clear Orange/Clear Green/Clear Yellow (depending on the color of the camera eyes)
Again, these served as references. It may not necessary has to be followed.
