ΔE 19.4, loose: different enough that you should pick on purpose. Brassy Brass is noticeably lighter, more saturated than Necron Compound.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Brassy Brass is noticeably lighter, more saturated than Necron Compound.
The same difference applies the other way round: Necron Compound is noticeably darker, more muted.
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 Necron Compound on the colour wheel See Brassy Brass on the colour wheel
All matches: Necron Compound equivalents · Brassy Brass equivalents