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The colors were selected by taking a still from the original story in which the waistcoat was prominently shown, and copying the colors into four carefully-formed stripes. The colors may, thus, be not one hundred percent as in the original. Also, the actual waistcoat had more of a faint plaid pattern than simple stripes. Still, this should be a good enough approximation for casual cosplay, fan films, and such, at least until something better comes along.
That aside, for best results with a Sixth Doctor costume I recommend using cotton silk. (For other purposes you're left to your own judgement.)