What if monsters came in a range of rainbow colors?
There’s an old saw in Doctor Who circles, apparently going back to the thirtieth anniversary documentary “More Than 30 Years in the TARDIS” (and perhaps the originally broadcast version, which lacked the “More Than”), when long-time script editor Terrance Dicks famously pointed out a de facto trend in design on the show: “The colour for monsters is green.”
It sounds a little odd, stated baldly that way, but upon reflection it’s clearly true. There are the Silurians and Sea Devils, Alpha Centauri, the Draconians, the Krynoids, the Rutans, the Jagaroth… The list goes on and on. And if any of the aforementioned can be argued to be anything other than green, it’s a muddy brown instead.
Occasionally we’ll see something further into the red part of the spectrum—the Zygons, for example—but other hues are distinctly lacking. Where are the bright yellow critters, or the blue ones? I guess we’ve had the golden Axonites in The Claws of Axos and the occasional blue-faced humanoid (e.g., Dorium Maldovar), but in the grand scheme of things, the pre-Hiatus palette in particular definitely trends to green.