ΔE 20.7, loose: different enough that you should pick on purpose. Radium is noticeably lighter, more muted, cooler than Hoplite Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Radium is noticeably lighter, more muted, cooler than Hoplite Gold.
The same difference applies the other way round: Hoplite Gold is noticeably darker, more saturated, 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 Hoplite Gold on the colour wheel See Radium on the colour wheel
All matches: Hoplite Gold equivalents · Radium equivalents