My attempt to bring the two halves closer together.
Each half was copied and pasted into a separate file and then separately
colour corrected to get the most neutral colours.
Then each half was copied back over the original as a separate layer and
a colour balance adjustment layer was added to each half for final adjustment.
The right half had its midtones adjusted for more green and less blue and
the left half had its midtones adjusted for more red and more blue.
The left half needed a some masking to slightly reduce the effect of the colour
balance adjustment in order to get the fleshtones closer to those of the right half.
The background still has a bit of a colour mismatch but the overall image
is more in balance than was the case in the original.