This is a real can of worms - coolant leakage noted on the MOT would probably be an external leak as they wouldn't know about it otherwise - (never had an MOT inspector look in the radiator cap or expansion bottle). Without added colour antifreeze would be colourless, the reason they put colour in anti-freeze is not to make it look pretty or to indicate what type it is (Glycol or OAT), but to show up any leaks.
if it has developed an air lock in the cooling system because of the leak that can make the engine temperature light come on, if the light comes on this time of year I would worry, never saw the light on my GD come on even on the hottest day in traffic. The fan should come on long before the warning light, and it would be easily heard. The one thing that I didn't like about the GD was the lack of temperature gauge, which would give early warning of developing problem, by the time the warning light comes on you already have a problem.
As VicW rightly says could be a hose (easy and cheap) the radiator (expensive) or it could be head gasket which would pressurise the system and blow coolant back past pressure cap into expansion bottle, blown gasket can also allow coolant into cylinder when engine not running, look for excessive water vapour (steam) from tail pipe when starting engine.
point to watch on early GD models is rear brake pipes where the go into the drum, these are prone to corrosion after 6 to 7 years and Honda will charge over £200 to replace 2 short lengths of pipe, this should have been picked up on MOT before now though. If it has drum rear brakes it is a good thing, as rear discs are more trouble than they are worth.
