I would have no difficulty playing a blue T-991 or a red Selmer Serie III tenor if one came along at the right price, but I don't fancy my chances of coming across the genuine article. Instrument colours are to some extent a matter of tradition. Brass bands like either gold or silver. These colours are less likely to clash with uniforms.
From what I can see, saxophones in colours other than variations of gold, silver and black by and large seem to be of the cheaper sort made in China. That in itself is not a problem, but I just wonder how long the lacquer or whatever would last. I have had Chinese fountain pens that looked great when I bought them and that quickly took on the camouflage look one associates with army needs.
Colin the Bear is of course right. A bright red saxophone would be ideally suited for presto or molto furioso passages. One in Killarney green would be the preferred choice for an adagio. Imagine the possibilities opening up to doublers.