Mutant Hue vs Trooper White

How close are they?

ΔE 21.5, loose: different enough that you should pick on purpose. Trooper White is a little lighter, more muted than Mutant Hue.

Can I use Trooper White instead of Mutant Hue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Trooper White is a little lighter, more muted than Mutant Hue.

Can I use Mutant Hue instead of Trooper White?

The same difference applies the other way round: Mutant Hue is a little darker, 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.