Putrid White vs UK Light Stone

How close are they?

ΔE 6.1, close: similar, with a visible difference side by side. UK Light Stone is a little lighter than Putrid White.

Can I use UK Light Stone instead of Putrid White?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). UK Light Stone is a little lighter than Putrid White.

Can I use Putrid White instead of UK Light Stone?

The same difference applies the other way round: Putrid White is a little darker.

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.