Ray
RI Modelers I know have used:
Santa Fe RED
Erie Lackawana MAROON.
Scalecraft II products formerly offered the true RI colors in their line, but the company was sold in 2015. The successor owner is now Minuteman Scale Models reachable by e-mail at: info@minutemanscalemodels.com or by phone at: 978-302-4524.
Tip : Beware of a maroon color that is too "grape" and a red color that is too "orange." A real RI diesel loco was repainted for a tourist RR, and the owners color-matched a vintage photograph of the train. Unfortunately, the photo dye colors were faded with age.
The "Full Rocket" RI paint scheme was created in 1937 for the TA diesel; it was a classic art deco design. Decades later, when the RR fell upon hard times, this design was simplied for the sake of economy -- and IMHO ruined.
Good luck with your project! Consider sharing pix of the finished loco on the OGR Forum for RI hobbyists to enjoy.
Mike