Iron Man vs Dechala Lilac

How close are they?

ΔE 32.3, loose: different enough that you should pick on purpose. Dechala Lilac is a little lighter, much more saturated than Iron Man.

Can I use Dechala Lilac instead of Iron Man?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 32). Dechala Lilac is a little lighter, much more saturated than Iron Man.

Can I use Iron Man instead of Dechala Lilac?

The same difference applies the other way round: Iron Man is a little darker, much 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.