Ww/W In the USA you must pass colour vision tests to get an unrestricted medical. For a CPL you need a class 2 medical and you can have the colour vision test done practically with an FAA official on an airfield. If you can tell the tower signal gun lights at 1000 and 1500 yards you get a SODA waiver (Statment of Demonstrated Ability) this acts as the colour vision part of your medical exam and gives an unrestricted medical. For an ATP you need a class 1 medical and will have to do a medical flight test at night with an FAA guy to be able to distinguish the runway lights, taxiway, other aircraft nav lights , beacon etc. This will give a SODA for a class 1 Med.
It is apparentley harder to get work though with SODA waiver. The FAA will also use lantern tests and if you pass these gives an unrestricted medical same as in the UK.
Have you done the City Uni test to see exactley where you stand?
Good luck with your flying and all the best.