Thunder Blue vs Orchid Light

How close are they?

ΔE 23.9, loose: different enough that you should pick on purpose. Orchid Light is noticeably lighter, more muted, warmer than Thunder Blue.

Can I use Orchid Light instead of Thunder Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Orchid Light is noticeably lighter, more muted, warmer than Thunder Blue.

Can I use Thunder Blue instead of Orchid Light?

The same difference applies the other way round: Thunder Blue is noticeably darker, 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.