Old Red vs Toxic Boils

How close are they?

ΔE 9.5, close: similar, with a visible difference side by side. Toxic Boils is more muted, cooler than Old Red.

Can I use Toxic Boils instead of Old Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Toxic Boils is more muted, cooler than Old Red.

Can I use Old Red instead of Toxic Boils?

The same difference applies the other way round: Old Red is more saturated, 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.