consider adding a warning to colourInput for reverting unsupported color

[romunov]

If palette = "limited" is selected and specified color is not in the (limited) list, it will revert to black. Would it possible to add a warning that the function has reverted to some prespecified color?

[daattali]

I don't think it's that bad of a behaviour. I wonder what happens if you create a selectInput() or radio buttons and provide a non-existent value? Anyway, I'm open to a PR if you'd like to add a simple error check for that

[romunov]

I was thinking alongside of a warning, just to give tinkerer a head's up. Or perhaps a sentence about this in the docs. I would consider falling back to some predefined color as perfectly acceptable.