Well, the sunshine_challenge may be over, but—looking over what I've written on the colours—I find I still have a bit more to say.

In the last post, on VIOLET, I took colours beyond the spectrum and round the colour wheel, finishing up where it all started, i.e. with RED. However, I had the devil of a job doing that last bit:

VIOLET					RED

Although the end points were fixed (and I knew that #FF00FF needed to be in the middle), I kept fiddling with the hex codes, tweaking them over and over in an attempt to get a smooth set of transitions. Even now, I'm not satisfied.

Thinking about it after the fact, though, I think I've put my finger on the problem. Something silveradept wrote:

It's interesting - when I imagine the platonic examples of colors (which usually involves a crayon box), almost all of the shades of the Newtonian spectrum are dark, with the exception of yellow,[...].

I grew up with a set of basic colours that were essentially derived from the subtractive primaries. Oh, there was RED (instead of magenta + yellow) and BLUE (instead of magenta + cyan); but, as one mixed more paints together, things got darker. People who think in terms of additive primaries—originally scientists in Optics, but nowadays particularly people dealing with computers—are accustomed to having colours get lighter as they're added together.

What this means in practice is that, instead of the sequence above, I ought to find it easier to get a gradation by using dark shades.

VIOLET	PLUM	PUCE		CRMSN		RED

Oh, yeah. Definitely.

It isn't only this sequence that grades oddly because of the difference between additive and subtractive colours. The same sort of thing happens between GREEN and BLUE. Sure, the "rule" is that GREEN + BLUE = TURQUOISE. However, adding two dark colours together "shouldn't" yield a much lighter one—well not if, like me, you're used to dabbling with paints, i.e. mixing subtractively.

GREEN		TEAL	PEACOCK	BLUE

So some of the seeming anomalies can be "fixed" by simulating the effect of subtractive colours, i.e. by using darker shades. Perversely, there is a different way to get a fairly smooth gradient—by not using pure shades at all. One can do it with pastels: pale shades of blue, green, and yellow; peach instead of orange; pink instead of red.

GREEN		AQUA		BLUE

BLUE		MAUVE		LILAC

LILAC	ORCHID			PINK

PINK	PEACH			YELLOW

YELLOW				GREEN

This has been fun! Much thanks to the organizers of the sunshine_challenge for coming up with the idea.