  This paper explores the quantitative connection between globular clusters and
the diffuse stellar population of the galaxies they are associated with. Both
NGC 1399 and NGC 4486 (M87) are well suited for this kind of analysis due to
their large globular cluster populations. The main assumption of our Monte
Carlo based models is that each globular cluster is formed along with a given
diffuse stellar mass that shares the same spatial distribution, chemical
composition and age. The main globular clusters subpopulations, that determine
the observed bimodal colour distribution, are decomposed avoiding a priori
parametric (e.g. Gaussian) fits and using a new colour (C-T1)-metallicity
relation. The eventual detectability of a blue tilt in the colour magnitude
diagrams of the blue globulars subpopulation is also addressed. A successful
link between globular clusters and the stellar galaxy halo is established by
assuming that the number of globular clusters per associated diffuse stellar
mass t is a function of total abundance [Z/H] and behaves as
t=gamma*exp(delta[Z/H]) (i.e. increases when abundance decreases).
