To change the survey colours first select the style area in which you wish to do it. In this example the style area is Desktop, but the settings are identical in all the style areas.
Click the Colors menu on the left to adjust the settings:
You can edit for example following Color sections:
Single choice & Multiple choice:
Tips & Tricks!
You can put RGB or hex values to the color picker. Just erase the current value and write e.g. rgb 255 255 255 and press enter to set the color.