Kislev Flesh vs Light Brown

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Light Brown is noticeably darker, more muted than Kislev Flesh.

Can I use Light Brown instead of Kislev Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Light Brown is noticeably darker, more muted than Kislev Flesh.

Can I use Kislev Flesh instead of Light Brown?

The same difference applies the other way round: Kislev Flesh is noticeably lighter, 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.