I will get a chance to see an IMAX print of TDK next month. I am not familiar with the Blu-ray colors, I didn't ever watch the Blu-ray, but I will be able to describe what I thought the IMAX looked like, just like I did with Begins.
Perhaps the Blu could be another case of regrading the untimed version almost from scratch to "read" better on the home medium - sort of like how even the original video transfer of The Matrix looks nothing like the theatrical prints.