So my next guess, which might even be valid probability theory, is that purple-white is more likely than purple-purple, and also more likely than that there is a single purple or white and I just happened to pick the one right colour from line one. All this for the viewers, and not an attempt to get extra information out of Idle Thoughts. 
So:
Yellow Purple Yellow White
X
History:
Interesting! So it’s not purple/white, then. Neither is it blue/purple (that would imply a code that was three blues and one purple, but then the third “peg” can’t be either blue or purple). The code either contains a triple purple or none at all - I can see only about four possible codes here, and as things have fallen out it could take three guesses to find the right one.
Purple Purple Purple Red
You got it. Impressive!
A lucky guess. It could have been Green Purple Purple Purple (which I’d’ve got next guess, obviously), or Blue {Blue/White} White White, which would have taken one or two more guesses. So the mean was two more guesses, and I was lucky to get it in one.
Want to take it to PMs? I think we’ve scared everyone out of the thread. 
No, I keep checking back, but I’m still trying to unlearn the way I used to play it. And it’s kinda frustrating to take turns with other guessers.
Is there any place to play this online, against a computer?
Well Neopets has it in their games. Just go to neopets.com and click on games and then on puzzle games and find the game of the same name. 
How about you think of the next code too, Robot Arm? It might help you learn this version too.