Tweetdeck allows its colour scheme to be altered easily. Click on Settings, then on the Colours/Font option. Click on the colour you want to change, then select the new colour from the palette displayed. You can also set a different font.

The toolbar icons have some illumination set by default and there's a slider which lets you change the brightness. There's even a Tweet Colors button which sends out a Tweet with the setting. Other users who use Tweetdeck might find these settings worth trying.