The green stuff might have been the VMX register files - those things were pretty huge (128 registers per thread, each register 16 bytes, so 212816=4 KiB per core). While the L1 cache was higher capacity (32 KiB) as a general rule of thumb faster memory uses more die area per bit.

But I seem to remember being told that the green areas were the VMX pipelines. I don't remember clearly, and the hardware people I asked at the time were uncertain - they were too far removed from that aspect of the hardware.

The other reason to assume that the blue is the caches is because it is closer to the cross-bar and the cross-bar is what connects the cores to the L2. Incoming data from the L2 goes first to the L1 caches so they would logically be on that side.