In some styles, the colors of the forums and categories are changed, to maybe red, etc.
Is there a way that I can change it with an html code when I create the forum?

To Change Color:

Admin panel
Display
Pictures and Colors on the left side
Colors

Then find what you want
Click on the color and change the color


For Categories:
General
Forum on left side
* Categories and forums
Create
When it asks for Choose the kind of forum you want : change it to Category
If you want it with a forum click do you want to add a Forum click yes
You can make a Catorgy with out the Forum and then click a forum and place it where you want it

To View Cotegories
Display
Index Packing
Pick the one you like

Hope This Helps

okey......