Have you checked in EXTRA.css that you didn't include the following or modified something by accident in SP.
Code:
.section {
background-color: #265F88;}
The above seems to be the culprit.
If your wanting to change the background-color change the color value box in Style Properties >> Forum/nodelist >> Category strip
You will also have to adjust the border colour values in the same area and text colour to your preference.
To change colour of the category titles go into Style Properties >> Forum/nodelist >> Categorystrip Title
To change colour of the category description go into Style Properties >> Forum/nodelist >> Categorystrip Description
You can reset the value on any areas you modified. Go back into the style properties categorystrips and you'll notice a checkbox in the top right. Make sure that is ticked and then update style and this will revert the changes you made and revert back to the default.
You're welcome but i don't think I helped much since you never managed to alter your categorystrip.
Kelvin if you still wanted to change your categorystrips and you want me to take a look at it (will have to be tomorrow) I'd need access to style properties. Feel free to send a pc if you want me to take a look tomorrow my time.