I thought it just always said 'splendid!' at the end. Tried twice, got both within six tries. I've paid attention to this sort of thing before, though. If I could get it close I'd generally have an idea as to what was left to change. I could see 'this is more red than it should be' and go from there.

Five games, number of tries to "Splendid!": 9, 4, 11, 19, 8

(Burnt orange, bright yellow, light blue, shock pink, dark blue)

So far I’ve gotten to the end for a few colors. Quite fun, took my about 20-30 guesses!

Fun! After a few game, my best was 100% on the 4th guess.

It looks like it's using Euclidean RGB difference, so one potential approach if you don't want to eyeball it is to just try to try to find the match for each channel one by one.

Edit: Okay, my new best score was 100% on the 1st guess, thanks to the browser inspector. :-)

8-12 attempts to get the color seems to be the range i tend to land in.

2 games, one was correct at the 27th try, the second one at the 14th.

First game: 77 % on the first try, Splendid! on the second.

i got 6. surprised that it was that few, I figured it would take forever.