True Copper vs Ancient Copper

How close are they?

ΔE 21.0, loose: different enough that you should pick on purpose. Ancient Copper is noticeably lighter, more saturated than True Copper.

Can I use Ancient Copper instead of True Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Ancient Copper is noticeably lighter, more saturated than True Copper.

Can I use True Copper instead of Ancient Copper?

The same difference applies the other way round: True Copper is noticeably darker, more muted.

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.