Hi @Jenny Franklin,
Having reached out internally, it would seem the only colours available for the Row Styles are those offered in the ribbon. If ncessary, please raise an enhancement request via Support for the Product Team to consider pallet code entries.
One thing I have found that you may find interesting is a function that allows you to change the colour of metrics in reporting. You can find the direction for this via the following Help Centre link:
https://help.apptio.com/en-us/studio/admin/set-default-colors.htm?Highlight=Set%20the%20default%20colors%20for%20project%20metrics
Hope this helps. Thanks Jenny.
Alex.
#ApptioforAll