ΔE 7.7, close: similar, with a visible difference side by side. Flat Yellow is more muted than Sun Stone.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Flat Yellow is more muted than Sun Stone.
The same difference applies the other way round: Sun Stone is more saturated.
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 Sun Stone on the colour wheel See Flat Yellow on the colour wheel
All matches: Sun Stone equivalents · Flat Yellow equivalents