That seems to be common for Red-Green colourblindness (of which I have an extreme form). My brother has a similar problem - red on blue or green causes the same dancing effect. I also get it for strong primary colours against blue, but I don't tend to perceive the non-blue colour - well, it is more complex than that as I shall try to explain.
If I see something colour (that isn't blue/violet), I can usually tell that it is not grey. However I simply cannot tell what colour it is other than it is lighter or darker.
My optician explained it like so. There simply aren't enough R/G receptors to give the old visual cortex enough information to resolve what the colour is, only that it is a colour and not simply grey (some very intense greens do register as different from everything else). As for unsaturated colours, they tend to look greyish.
Hence no need for me to suffer the work of interior designers :lol:
