You are given three sample liquids-ink,sand in water,saline water.

We can see the samples under a powerful microscope. the sand particles are visible to naked eye.

The particles of salt solution are not visible even under powerful microscope, while that of ink can be seen under the microscope

The sand from the solution will settle down if left undisturbed while the ink solids can be made to settle on centrifugation

The salt from saline solution will not settle

So

Ink is a colloid, sand in water is an example of suspension while saline water is a true solution