Indian Shadow vs Purple Shadow

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Purple Shadow is a little darker, cooler than Indian Shadow.

Can I use Purple Shadow instead of Indian Shadow?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Purple Shadow is a little darker, cooler than Indian Shadow.

Can I use Indian Shadow instead of Purple Shadow?

The same difference applies the other way round: Indian Shadow is a little lighter, 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.