Inner Light vs Marigold Yellow

How close are they?

ΔE 21.5, loose: different enough that you should pick on purpose. Marigold Yellow is noticeably darker, warmer than Inner Light.

Can I use Marigold Yellow instead of Inner Light?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Marigold Yellow is noticeably darker, warmer than Inner Light.

Can I use Inner Light instead of Marigold Yellow?

The same difference applies the other way round: Inner Light 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.