Deep Red vs Mars Red

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Mars Red is a little darker, more muted than Deep Red.

Can I use Mars Red instead of Deep Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Mars Red is a little darker, more muted than Deep Red.

Can I use Deep Red instead of Mars Red?

The same difference applies the other way round: Deep Red is a little lighter, more saturated.

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.