Shyish Purple vs Nightshade Purple

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Nightshade Purple is a little darker, much more muted than Shyish Purple.

Can I use Nightshade Purple instead of Shyish Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Nightshade Purple is a little darker, much more muted than Shyish Purple.

Can I use Shyish Purple instead of Nightshade Purple?

The same difference applies the other way round: Shyish Purple is a little lighter, much 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.