Space Red vs Worn Red

How close are they?

ΔE 15.8, loose: different enough that you should pick on purpose. Worn Red is noticeably lighter, more saturated than Space Red.

Can I use Worn Red instead of Space Red?

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

Can I use Space Red instead of Worn Red?

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