Question

how would you separate a mixture of different watercolour paints​

Answer 1

If it's rock hard, put a drop or two of water in it, perhaps a drop or two of glycerine as well, then massage it as best as you can, you can also stir it a bit with a paper clip, just be sure not to puncture the metal of the tube.

Answer 2

COLOR CHROMATOGRAPHY

By color chromatography, we can separate different watercolor paints.

Chromatography is one of the simplest techniques for separating the individual components of a mixture.  In chemistry, a mixture is a combination of substances that can be separated because they are not chemically bonded. In paper chromatography, a mixture is dissolved and pulled across a piece of paper.  The mixture separates because its components travel across the paper at different rates, based on their attraction to the paper or solubility in the solvent.

• When the water passes through the black ink it takes the pigment colors with it. Some pigments dissolve in water easier and are pulled with the water farther up the paper. This is called chromatography - separating the parts of a mixture so that you can see them one at a time. Black ink actually looks like a rainbow!
• Most watercolor marker inks are colored with synthetic color molecules. Artists often like to work with natural dyes. It is fairly easy to make your own dye from colorful plants such as blueberries, red beets, or turmeric.
• Be sure to always choose a solvent that dissolves the material that is being tested to run the chromatography test. Isopropyl rubbing alcohol, vegetable oil and salt water are some examples of solvents used to perform paper chromatography tests for different substances.