Ok I've done some testing with these today and discovered that the separate relay is not required because the bulbs have one already built in so that only one colour activates at any given time. Also when they say 48x or 60x LEDS they mean of EACH colour, each one does both so they're brighter than I was expecting which is great for the fogs and not a bad thing for the reverse light purposes.
But back to the colour switching...
What I wanted to do was for the White light to have power of Veto over the red, so that if the fogs were on and you put the car in reverse the white light would take over for a short period. However these are not made that way. The Red Fog light has Power over the White reverse light, meaning if I put the rear fogs on I have no reverse lights.
Now, I can't see this actually being a problem in normal use, even for a regular car but especially for the IROC which doesn't see much bad weather driving (especially in reverse), but I was wondering if it would be an issue for legalities.
Anyone know?
I've also had to modify the bulb holder slightly to make it fit (I cut the new holder @ £3 each instead of changing my light housing @ £150 each), its a simple change with some careful use of a modelling knife and still allows 3 locating tabs to grip the holder, just one of them is quite small now. Job done