Gemstone Red vs Miami Sunset

How close are they?

ΔE 36.1, loose: different enough that you should pick on purpose. Miami Sunset is noticeably lighter, cooler than Gemstone Red.

Can I use Miami Sunset instead of Gemstone Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 36). Miami Sunset is noticeably lighter, cooler than Gemstone Red.

Can I use Gemstone Red instead of Miami Sunset?

The same difference applies the other way round: Gemstone Red is noticeably darker, 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.