Orchid vs Warlock Magenta

How close are they?

ΔE 16.5, loose: different enough that you should pick on purpose. Warlock Magenta is a little darker, more muted, cooler than Orchid.

Can I use Warlock Magenta instead of Orchid?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Warlock Magenta is a little darker, more muted, cooler than Orchid.

Can I use Orchid instead of Warlock Magenta?

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