ΔE 13.9, fair: the same colour family, but not a straight swap. Obsidian Black is much more muted than Radiant Platinum.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Obsidian Black is much more muted than Radiant Platinum.
The same difference applies the other way round: Radiant Platinum is much 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 Radiant Platinum on the colour wheel See Obsidian Black on the colour wheel
All matches: Radiant Platinum equivalents · Obsidian Black equivalents