Glittering Loot vs Copper Coin

How close are they?

ΔE 17.2, loose: different enough that you should pick on purpose. Copper Coin is noticeably darker, warmer than Glittering Loot.

Can I use Copper Coin instead of Glittering Loot?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Copper Coin is noticeably darker, warmer than Glittering Loot.

Can I use Glittering Loot instead of Copper Coin?

The same difference applies the other way round: Glittering Loot is noticeably lighter, 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.