>>11569427
If you want clear saliva, get Games Workshop's (the Warhammer people) technical paint 'ardcoat. It's a gloss varnish that when applied in multiple coats makes a great clear gross slime. The pic is a model covered in 100 coats of the stuff.

If you want green saliva, they also make something called Nurgle's Rot. Which is the same as 'ardcoat but tinged a sickly green.