Pastel Lavender vs Undead Dragon

How close are they?

ΔE 31.6, loose: different enough that you should pick on purpose. Undead Dragon is much more muted, warmer than Pastel Lavender.

Can I use Undead Dragon instead of Pastel Lavender?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Undead Dragon is much more muted, warmer than Pastel Lavender.

Can I use Pastel Lavender instead of Undead Dragon?

The same difference applies the other way round: Pastel Lavender is much more saturated, cooler.

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.