Thunderbird Blue vs Hexwraith Flame

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Hexwraith Flame is noticeably darker, more saturated, warmer than Thunderbird Blue.

Can I use Hexwraith Flame instead of Thunderbird Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Hexwraith Flame is noticeably darker, more saturated, warmer than Thunderbird Blue.

Can I use Thunderbird Blue instead of Hexwraith Flame?

The same difference applies the other way round: Thunderbird Blue is noticeably lighter, more muted, 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.