none of the native poser 5 shaders were physically correct IIRC. 

try to fix it so that sum (diff+spec+trans+refl+refr) <= 1.0.

for thick glass,  refract and reflect node plugged into edge blend node (if P5 had those) plugged into alt_diff channel might look o.k., compared to fresnel set-up we now use.  for thin glass, edge blend node into trans channel and reflect node into reflect channel or alt_diff channel may look o.k.

coloured glass is more difficult, but maybe varying edge blend colours would work as simplified gem/thick glass shader in P5, which I've still got on an old computer but I dread using it.  I just tried P4 on it and nothing went wrong, but P5 was unstable (trying to recall the nightmares of 10 yrs ago in whatever OS X was current, something like cheetah, named after tarzan's crazy chimp), whilst P4 was not.