Here the idea of having a reverse gradient as the fill is tried. The shapes are combined to a compound path and 180 degrees rotated gradient is applied. The gradient is global:
Not especially good! Very low contrast and shapes, which are side by side with no space, seem to be one.
Let's copy the original shapes onto the gradiented ones and reduce the transparency:
The opacity of the original shapes is 14%. That seems to be useful, but the contrast is still low if we want to have "nearly reverse gradient fill"
Another option is to make the gradients individual (=no compound path, the originals are removed from the top)
This helps the "be as one" problem and dosn't increase the colour range. But the contrast is still weak. Clearly seems to make the shapes to look out as curved.
The last test is to have a three stop gradient, brightest in the middle and a little extended to the dark end
This seem to be a bunch of cylinders. Maybe unusable. I would continue to develop version 2.
NOTE if you have strokes, outlining them make colorings faster to do.
ADDENDUM: An improved version of 2 - this is for making more contrast, not to reduce it:
Here on the top there are the original shapes, but they have the blending mode = Hard light. Underlying there is a grey gradient, from about 75% white to black. Starting from full white washes the colors too much. The gradient fills a compound of the original shapes.