Bright Red vs Scarlet Red

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Scarlet Red is noticeably darker, more saturated than Bright Red.

Can I use Scarlet Red instead of Bright Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Scarlet Red is noticeably darker, more saturated than Bright Red.

Can I use Bright Red instead of Scarlet Red?

The same difference applies the other way round: Bright Red is noticeably lighter, more muted.

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.