The number of colloidal systems from the following, which will have 'liquid' as the dispersion medium, is ______.
Gem stones, paints, smoke, cheese, milk, hair cream, insecticide sprays, froth, soap lather

We need to identify how many of the given colloidal systems have liquid as the dispersion medium.

First we classify each colloidal system: Gem stones involve a solid dispersed in a solid, so the dispersion medium is solid (✗); paints involve a solid dispersed in a liquid, so the dispersion medium is liquid (✓); smoke involves a solid dispersed in a gas, so the dispersion medium is gas (✗); cheese involves a liquid dispersed in a solid (a gel), so the dispersion medium is solid (✗); milk is a liquid dispersed in a liquid (an emulsion), so the dispersion medium is liquid (✓); hair cream involves liquid or solid dispersed in a liquid (an emulsion or sol), so the dispersion medium is liquid (✓); insecticide sprays involve a liquid dispersed in a gas (an aerosol), so the dispersion medium is gas (✗); froth consists of gas dispersed in a liquid (a foam), so the dispersion medium is liquid (✓); and soap lather consists of gas dispersed in a liquid (a foam), so the dispersion medium is liquid (✓).

The colloidal systems with liquid as the dispersion medium are paints, milk, hair cream, froth, and soap lather.

Therefore, the number of colloidal systems with a liquid dispersion medium is $$5$$.