Category font size.

Good day all.
I please need assistance to increase the font size on my sub categories and also to underline the parent category of my categories.

I tried to use the function <u>category heading</u> and also <font color=”######”>category heading</color> with no success.
To increase the font size for the sub category i tried <font size=”4″>sub category heading</font>

With all of the above I had no luck.

Do I need to do this in Custom Meta Data and if so how do I go about it.
I found a similar post in the support forum and tried it and could not get a solution to my problem.
thank you.