Change Colours Of Modules

Is there an easy way to change the colour of the modules, using the 'Module Class Suffix'?

yes,

example:

suffix = " red"


in css:

.red{
backgorund-color:#FF0000!important;
}

Thanks, but which file does it go into?
template_css.css
layout.css
joomla.css

template_css.css is recommended, any will do.

I must be doing something wrong!

I have put it in all of the files and entered:
red
-red
.red
_red
as the Module Class Suffix and nothing changes!

FYI, I am using a custom HTML and Acymail module.

there is one blank char at start in suffix value, to explain:

without suffix:

<div class="normal"

with suffix:

<div class="normalsuffix"

you add blank at start so you would get:

<div class="normal suffix"

so you can style example div using:

.suffix{...