Here is the reply from the NAM.
Enquiry: Identification of Uniform and Badges
Thank you for your e-mail dated 10 December 2007, which has been forwarded to me for a reply.
From the detailing visible in the image forwarded I think it most likely that your ancestor was serving in the 96th when this portrait was painted. The 94th had Green facings (collar and cuffs) whilst the 96th had yellow. The arm badge is that of a Colour Sergeant I believe it is pre 1866, from then the badges were worn on both arms.
Rifle Volunteers generally wore green uniforms; the City of Norwich Rifle Volunteers did wear green, however, I have been unable to confirm the colour worn by the Attleborough Rifle Volunteers. Neither can I find conclusive evidence of the uniforms worn by the West Norfolk Militia.
I believe the number 90 refers to your ancestors regimental number rather than his service number.
For further information on the Volunteer and Militia Regiments you may wish to contact the Royal Norfolk Regimental Museum, Norfolk Museum Services, Shirehall, Market Avenue, Norwich, NR1 3JQ. E-mail museums@norfolk.gov.uk For the 96th you should contact the Museum of the Manchesters, Ashton Town Hall, Market Place, Ashton-under-Lyne, OL6 6DL e-mail portland.basin@mail.tameside.gov.uk
I do hope the above information proves to be of interest for your research.
Yours sincerely
Mrs G Brewer
Curator, Department of Uniforms, Badges and Medals
I'm now even more confused!!!