I'm sure no one is disputing the role of color in typography per se. Color fonts as letters constructed with several colors within every letter is different though. This breaks the idea of positive and negative shape that is so inherent to type. As you point out, this can be interesting exploration, and the examples you show have a visual novelty to them.Mark van Wageningen / Novo Typo said:
The reason to use color was to introduce hierarchy in the layout of the page. Later on color was often used to separate paragraphs with a colored pilcrow ¶ or a colored silcrow §. This brings us to the second direction in which color is used within typography.