Colloid is not a substance but a state of substance is a true statement because some substances which are crystalloids under certain conditions can be colloids under the other, e.g.
NaCl is a crystalloid in aqueous medium, but when mixed with benzene, it behaves as a colloid. It is the size of the particles of that matter, i.e. the state in which the substance exists. If size lies in range of 1-1000 nm, it is in the colloidal state. So, above statement is true.