Ok... that sounds very simple to do, just take a look at the examples application: RibbonBar / First Look on how to create the color / color chooser element - This should be enough to create the ribbon components necessary for this operation.
After that you will have to register to the grid's CellFormatting
event (I believe that there are a lot of examples on the forums on how to use these) and set the appropriate colors based on the users selection.
One other thing, for the grid to apply the selection you should add these two lines:
// maybe do some other things
Hope this helps, if you have any other questions or comments, please let me know,
Telerik WinForms MVP