Well I've not noticed that previously but you do appear to be correct:
Assuming you are talking about the Album Covers (or Artists) view then, when the track list panel is over a certain size, the 'auto-pick panel colours' change from a blurred album cover to a solid colour. On my setup this seems to be a single column list of 55-56 tracks (I don't have any album large enough to check with 2 columns). There may well be other variables that affect this threshold point.
There is certainly no option to control this.
I think that you would be justified in reporting this as a bug to see if Stephen would be willing to have look (although I do imagine this is quite a rare album size/layout combination).