[en] If quarks are coloured and interact by exchanging gluons, this has simple implications on the mechanism which mixes q antiq pairs inside neutral mesons. These implications seem to be verified in first approximation for the masses and quark compositions of the pseudoscalar, vector and tensor mesons. The experimental intensity of the mixing is particularly weak for vector mesons, which have negative C-parity, as expected. In the general case, the exception being the pseudoscalar mesons, the mixing process is of small amplitude. It is then the mass hierarchy of quarks which governs essentially the composition of neutral mesons