No need at all to apologise, Roddy. I take all this colour symbolism with a pinch of salt, but let me give a try. The yellow is the gorse on Bodmin Moor or round Land's End. The green (the predominant colour) for the heather. The blue for the sea which surrounds Cornwall on every side.

I'm looking down at my kilt now and, honest Rodders, I can't see any yellow or gold. I'll look again in the morning.