Couldn't be more wrong. It's sold way more than Colours ever will.
Are you sure about that? The last reported figure for Colours was up to 2.18 million based on the FY2011 report.
http://www.neogaf.com/forum/showthread.php?t=430095
I mean we have a joke data from tssz that puts generations at 1.6-1.7 (Lower than Colours in a similar timeframe) million from ********, but we don't have any real data that I'm aware of.
Sonic Unleashed hit a total of 2.45 Million, and that number is, if statements are to be believed, largely thanks to the Wii version.
http://www.tssznews.com/2009/05/18/sonic-unleashed-segas-3rd-best-seller/
We'll have to see what numbers Generations manages to get to with only the traditionally weaker 2 console platforms for sales, but I'd be surprised if the manage to keep pace with Colours, and there's certainly no chance that Generations has already sold more than Colours ever will.