ΔE 11.3, fair: the same colour family, but not a straight swap. Sun Yellow is a little darker, warmer than RLM 04 Yellow.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Sun Yellow is a little darker, warmer than RLM 04 Yellow.
The same difference applies the other way round: RLM 04 Yellow is a little lighter, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See RLM 04 Yellow on the colour wheel See Sun Yellow on the colour wheel
All matches: RLM 04 Yellow equivalents · Sun Yellow equivalents