Spartan Bronze vs Ruby Red

How close are they?

ΔE 40.1, loose: different enough that you should pick on purpose. Ruby Red is noticeably lighter, much more saturated, cooler than Spartan Bronze.

Can I use Ruby Red instead of Spartan Bronze?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Ruby Red is noticeably lighter, much more saturated, cooler than Spartan Bronze.

Can I use Spartan Bronze instead of Ruby Red?

The same difference applies the other way round: Spartan Bronze is noticeably darker, much 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.