Aztec Gold vs Summoning Sickness

How close are they?

ΔE 20.8, loose: different enough that you should pick on purpose. Summoning Sickness is a little darker, much more muted than Aztec Gold.

Can I use Summoning Sickness instead of Aztec Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Summoning Sickness is a little darker, much more muted than Aztec Gold.

Can I use Aztec Gold instead of Summoning Sickness?

The same difference applies the other way round: Aztec Gold is a little lighter, much 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.