Tap for any Color?

[SpiritedAway]

I've always wandered, by super duper official MTG rules, when a card reads "Name a color" "color of your choice" or the like, can you name really name any color? Such as magenta, vermillion or burnt sienna?

I only wander because I often play a card called {Blessed Breath} with my friends for random other effects (like {oyobi who split the heavens} and {quillmane baku}) so the protection doesn't matter really. I do it as a joke, but it gets me thinking...

[Spikepit]

Everything in MtG can only be directed towards legal targets, so no Vermillion. ðŸ˜,

Which is a shame coz I've made a few purple cards before. Lolz.