Ultegra 6700 Left Side Crank with SRAM Red
Speaking under correction, because I don't know the exact model, but have owned Shimano &amp; SRAM in the last few years.  The two systems aren't compatible to the point that you can just swap the left side crank.

But, you will be able to swap both sides.  In other words, once you've taken the left side off, the right side, with chainrings and all should just slide out.  You can then put the whole shebang onto the other bike.  As long as the chainrings are the same size (i.e. 53x39) you won't need to move the front deraileur to accommodate the change.