ΔE 24.1, loose: different enough that you should pick on purpose. Radium is noticeably lighter, more saturated, cooler than Retributor Armour.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Radium is noticeably lighter, more saturated, cooler than Retributor Armour.
The same difference applies the other way round: Retributor Armour is noticeably darker, more muted, warmer.
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 Retributor Armour on the colour wheel See Radium on the colour wheel
All matches: Retributor Armour equivalents · Radium equivalents