MIL-STD-104 Revision C, October 31, 1986
LIMITS FOR ELECTRICAL INSULATION COLOR
Additional Comments: SEE ALSO APN A**SUPP 1 CONTAINED IN EIA-359 SET
Class 1 colors are applicable to all insulation materials which will accept bright, highly saturated (high chroma) pigments. In general, plastic insulations intended for use where exposure to direct sun-light is infrequent can be furnished in Class 1 colors. Wherever possible, Class 1 colors are preferred to Class 2 colors and should be specified. Violet may be used where purple is specified.
Class 2 colors are applicable to all insulation materials which will not accept Class 1 colors particularly where color permanence is a factor. In general, fabric and rubber materials may require use of Class 2 colors, although Class 1 colors should be specified if their use is practicable.