Evil Eye Red vs Flat Red

How close are they?

ΔE 19.6, loose: different enough that you should pick on purpose. Flat Red is noticeably darker, more saturated, cooler than Evil Eye Red.

Can I use Flat Red instead of Evil Eye Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Flat Red is noticeably darker, more saturated, cooler than Evil Eye Red.

Can I use Evil Eye Red instead of Flat Red?

The same difference applies the other way round: Evil Eye Red is noticeably lighter, 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.