This suggestion is general and not specific to this particular table.

I agree. I would replace that colour all together.

Also the Grey Player Meeple is hard to see on the Trail. I realize the real game used white, but for online, another primary color would be better.

Also, if you're not going to change this, at least make white the last color chosen. Every time I have played this game with 2 players, I have gotten assigned white/grey. And I'm not a premium member, so it's not my chosen color.

It seems like you've solved with problem (quite nicely!) with the "turn white things purple" option. I think the problem is that players don't know that's what the option does. I realize there are space (and language) restrictions - maybe "White player pieces > purple" instead of "white material > purple"? (I haven't noticed if the option does anything else.)

I think you should make this the default setting. White is often a terrible choice for player color for online gaming because it's so hard to tell an empty space from a white marker (black very frequently has the same problem). I understand the desire to recreate the physical game, but this is just a case where online play requires different solutions.

(Sometimes it's a problem with physical versions of games as well, especially if the board if very busy. There are a number of BGG threads with players talking about marking or repainting figures so they're easier to distinguish. I've also heard from people involved in the process that it can be very difficult to get colors produced with exact color specifications, so sometimes they're surprised or disappointed with how a game comes out.)