Thanks for the quick reply! I have looked at the menu item wich displays the subscription plans, but I can't find a parameter called "Standard plan background color" (in fact no parameter with color). Mayby I'm looking in the wrong place? (See screenshot)
(Also in the linked article (number 118 from the screenshot) is no reference. Youtheme is used for this website.)
Can you send a picture, where to look for this option?