Hobgoblin Hue vs Frostbite

How close are they?

ΔE 18.3, loose: different enough that you should pick on purpose. Frostbite is a little lighter, more muted than Hobgoblin Hue.

Can I use Frostbite instead of Hobgoblin Hue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Frostbite is a little lighter, more muted than Hobgoblin Hue.

Can I use Hobgoblin Hue instead of Frostbite?

The same difference applies the other way round: Hobgoblin 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.