ΔE 26.9, loose: different enough that you should pick on purpose. Caesar Red is noticeably lighter, more muted, cooler than Gemstone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Caesar Red is noticeably lighter, more muted, cooler than Gemstone.
The same difference applies the other way round: Gemstone 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 Gemstone on the colour wheel See Caesar Red on the colour wheel
All matches: Gemstone equivalents · Caesar Red equivalents