This gets philosophical:
Apparently both, the colour and Blue are nouns (capital B in English?) in "Culoarea este albastru": culoare f., albastru n.
The abstract property of colour of some unspecified object is no substance, and thus cannot visually appear blue itself, but it can be specified as the equally abstract concept of Blue. Only the corresponding object that has this colour Blue (noun) is itself blue (adjective).
"Coloarea este albastră (adjective)" would however mean that "the colour" refers to some material colouring substance like paint or watercolour that appears blue as an visible object itself. Right?
Thanks, yes, you can state the grammar more concisely. But I find it still remarkable, that when you use the adjective, you are talking about a substance. So: "The colour of the crayon is white (adj. like fresh)" is strictly referring to the paint on its outside or the pigments used in the inside - while "The colour of the crayon is white (noun like Monday)" is referring to an abstract property of the object. So "colour" has two different meanings here.
(But whether you enjoy this kind of nitpicking is another matter, of course :-)