ΔE 6.1, close: similar, with a visible difference side by side. Evil Sunz Scarlet is a little lighter than Imperial Red.
Can I use Evil Sunz Scarlet instead of Imperial Red?
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Evil Sunz Scarlet is a little lighter than Imperial Red.
Can I use Imperial Red instead of Evil Sunz Scarlet?
The same difference applies the other way round: Imperial Red is a little darker.
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.