how do I know the main color of jersey?

[Poker-32]

The design color or the stripe color is the secondary color..

During matches your 'update-line' (where you can read the commentary) will be a white background (primair color) with blue words (secondary color)

[Hear_break_kid]

During matches your 'update-line' (where you can read the commentary) will be a white background (primair color) with blue words (secondary color)

Agreed