You can only manipulate things of your nation's color. It would be best, when in other lands, to carry weapons and supplies with those colors.
Also, you'd do well to wear clothes with those colors, as they can also channel your psychic force through them to augment strength, durability and other physical attributes.
The strength of your telekinetic/psychic power determines how much force you can exert. You'll come across stronger color manipulators, colors you can't manipulate and plenty of monsters and interesting landscapes, so it won't be easy all the time.
Not to mention, some can extend their color based powers into other forms (telepathy with anyone wearing their color, touching something of their color to pick up psychic imprints, etc), locating things of their color, etc.
Each of us gets to choose one auxiliary power aside from telekinetic manipulation of our color.
EX:
Character: Violet
Color: Violet/Purple (means she can manipulate anything that's purple)
-Sub-Power: Violet/Purple Teleportation (can teleport to any place where purple is the dominant color, and can teleport purple things to and from herself)
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)