In the /usr/share/themes/"Theme_You're_using_Name"/gtk2.0/gtkrc
Open the gtkrc file in root, then change this part:
base[NORMAL] = "#FFFFFF"
... it will change the color of your mousepad app (the part that you write on), as well as the color of those "gray" lines in Thunar.
I would suggest changing it to this so it matches your browser:
base[NORMAL] = "#FBF8F1"
Whatever color you use for base normal, will also make two darker shades of that color for the stripe colors (same palette). Then, if you change the colors for:
base[ACTIVE] - will be for the color of the last folder that you were in.
Example: If you're in /home/pmd/net and you have clicked on the 'net' folder in the right side of your Thunar app, the color of the Highlighted 'pmd' folder in the left (shortcuts) side is base[ACTIVE]. If you click bake to 'pmd' (now selected), the 'net' folder becomes the active color.
base[SELECTED] - is for the color of the folder you select (the one you've clicked onto).
Example: If you're in /home/pmd/net and you have clicked on the 'net' folder in the right side of Thunar, the color of the Highlighted 'net' folder in the right is base[SELECTED]. If you click back to 'pmd', it becomes the selected color.