Hi Mike,
in the Austin Healey restoration bible(Anderson and Moment restoration guide)
only the available paint,trim colors and combinations are mentioned at page 41.Not the ICI paint codes.
The Reno Red ICI code number for your 100 BN2 is 3000,
as stated in the"Original Austin-Healey 100,100/six and 3000" restorer's guide by Anders Ditlev Clausager at page 49.
Regards
Fer