Here is what you need to do to match the current portal theme "renewal":

1. Create a file called renewal.skin.properties and place it in your RichFaces applications WEB-INF/classes folder or package it into a jar.

2. Place the following in your renewal.skin.properties file:

#Colors
headerBackgroundColor=#4b6ca3
headerGradientColor=#2e4f86
headerTextColor=#ffffff
headerWeightFont=bold

generalBackgroundColor=#FFFFFF
generalTextColor=#000000
generalSizeFont=12px
generalFamilyFont=Tahoma, Verdana, sans-serif

controlTextColor=#000000
controlBackgroundColor=#ffffff
additionalBackgroundColor=#FFFFFF

shadowBackgroundColor=#000000
shadowOpacity=1

panelBorderColor=#C0C0C0
subBorderColor=#ffffff

tabBackgroundColor=#dcdcdc
tabDisabledTextColor=#dcdcdc

trimColor=#dcdcdc

tipBackgroundColor=#dcdcdc
tipBorderColor=#dcdcdc

selectControlColor=#dcdcdc

generalLinkColor=#0078D0
hoverLinkColor=#0090FF
visitedLinkColor=#0090FF

# Fonts
headerSizeFont=12px
headerFamilyFont=Tahoma, Verdana, sans-serif

tabSizeFont=12
tabFamilyFont=Tahoma, Verdana, sans-serif

buttonSizeFont=12
buttonFamilyFont=Tahoma, Verdana, sans-serif

tableBackgroundColor=#FFFFFF
tableFooterBackgroundColor=#cccccc
tableSubfooterBackgroundColor=#f1f1f1
tableBorderColor=#C0C0C0

3. Place the following param in your web.xml:
<context-param>
<param-name>org.richfaces.SKIN</param-name>
<param-value>renewal</param-value>
</context-param>

4. Read more about it here and post on the forum when you are done.
http://www.jboss.org/file-access/default/members/jbossrichfaces/freezone/docs/devguide/en/html/ArchitectureOverview.html#CreatingAndUsingYourOwnSkinFile

This is what the result will look like: