Hi!
Where ein the css editor can I find where I can change the backgrounds in the tinyrocket template (both on the top, the grey, and the gray/white futher down). I can't find it.

Thank you in advance!

Hi!
You will find the corresponding CSS classes in the following file (in your Joomla root directory):
/templates/tinyrocket/subthemes/tinyrocket/custom.css

Download the custom.css file via FTP and open it with your prefered HTML/CSS editor.

This class is responsible for the overall background color (the light grey/blue):
body {font-family: 'Questrial', sans-serif; border-top:3px solid #1d2024; background-color:#e6ecf3;text-shadow: 0 1px 1px #fff;}

Edit the "background-color" value to change it.

This class is responsibel for the header area (dark blue background color):
.top_wrapper {background-color:#31373d; float:left; width:100%; background-image: url(images/dotted.png);margin-bottom:20px;border-top:1px solid #3d444b; }

It uses the "background-color" and "background-image" value for the background.

Thank you for the answer!
I've changed it, svaed it as "custom.css" and written over the old file with Fliezilla. Still I can't see any change at my website when I update it. Do I have to activate anything on the website to see the changes?

Hi, no, normally not.
It can be that you have to clear your browsers cache fitst, or, if you have activate the Joomla cache memory, wait till a new refresh (default setting every 15 minutes, but depends on your settings).

And type the direct URL to the css file into your browser bar to see if there is the new or old file. Just to make sure the old one was really replaced...