why? a cation is positively charged, with more protons than electrons, an anion is negatively charged with more electrons than protons....i fail to see what color has to do with any of that? most metals and alkali earths from cations, so silver or gold would be more appropriate, while anions are formed by halogens and nonmetallic compunds, which if heated, release a greenish light. most compounds that contain cations will produce a reddish/orange color. Copper is an exception, producing a green light
I reasoned it out this way: Metals form cations by losing their outermost valence electrons to obtain a full outer shell of electrons. Metallic oxides (from cations) are basic, and and turn red litmus blue. Reactive metals also react with cold water to form a metal hydroxide, which turns universal indicator blue. Hence Cation material is blue in color. Non-metallic oxides (from anions) are acidic and turn blue litmus red, hence Anion material is red in color.
Love all the chemistry here... but maybe it's just because it would match the colors that Cosmic Boy turns you in HQ Orientation (elite)... Nah... couldn't be that simple.
It seems to me that the author of the topic has in mind that the traditional designation in electrical devices is red for a wire with a plus, and blue for a wire with a minus ... but maybe it depends on the country ...