Is it possible to increase the saturation of one color only in VSE?
i would use The Gimp
open the image and open the hue tool
then select the color you want to increase
In the ‘N’ panel, go down to Modifiers and select the Hue Correct modifier. In the H,S,V buttons, make sure the S is selected. In the color chart, select whichever dot is closest to the color you want to change and raise it upward to increase Saturation.