The colors of the skills don't mean anything in respects to caps. They just show different levels of numbers and have no effect.
To figure up caps:
INT, Teamwork, and Consistency do not change and are capped immediately.

Stamina caps at 20 for all players.

Speed and Strength have a variable hard cap. Without a supporter account, the only way to find the caps for these are focus train on one of the skills and track the training each week. Using the formula in the FAQ, determine the maximum number of weeks needed to ensure the skills should increase. Once you focus train for that many weeks, if the skill has not increased, it is capped. Example. 20 fitness coaching, max fitness center, and player with teamwork of 19 or 20 will get a minimum of 34 training points towards focused speed or strength. This means the skill should increase every 3 weeks. If you've focused trained speed or strength for 3 consecutive weeks and the skill has not increased, then the skill is capped.

Other skills (positioning, vision, footwork, carrying, tackling, blocking, passing, catching, kicking, punting, and agility)
multiply the number of talent stars by 2 and add 10 to find the soft cap for these skills. The skills still have a chance to increase above this until it reaches the hard cap, which is 3 above the soft cap. Example, 2 1/2 star talent player will have a soft cap of 15 ((2.5*2)+10) and a hard cap of 18 (15+3).

Hopefully, I haven't messed something up in this or forgotten something.