Unfortunately, I haven't come across any serious research into how three-spot gourami genetics work. If I had, I'd be all over that info right now - I LOVE genetics
Without going into detail, it would be rpetty much impossible to rpedict what your fry will turn out as without knowing exactly what kind of genes the parents carry (their 'genotype') but, basicaly, color genetics are usualy governed by dominant genes (strong ones), recessive genes (weak ones) or polygenes (several genes that all work together and can result in in-between colors). Dominant (strong) genes, mask/hide recessive (weak) genes most of the time. In other cases, you get some of the weaker geen showing through so it has some effect on the appearance of the organism (appearance is 'phenotype'). The thing about these is that, without experimenting with several breedings with different fish and also crossing their offspring, it's impossible to tell which color is caused by which type of gene.
From what I do know, the '3-spot' color is dominant so usualy prevails over the 'opaline' pattern. However, that doesn't mean 2 '3-spots' can't produce an opaline as the parents can be carrying the opaline color as it's caused by a recessive (weak) gene.
Also, the 'natural' color of the three-spot gourami is an olive-brownish shade (probably what you are getting). The 'blue' we are all so familiar with was selectively bred. As such, this clear 'blue' color is probably caused by polygenes. It is, as such, extremely easy for fry to revert to this 'wild' color if the parents are not both clear blue fish. That's why many spawning are likely to result in that kind of color.
The gold color, as far as I'm aware, is a mutation. As it occurs in the wild, it makes sense for crosses of golds with 'domestic' blues to produce the 'wild' color as the ancestors of golds are likely to carry the genes responsible for that brown color. As I suspect this to be caused by recessive alleles, I'd expect a gold X gold cross to only produce golds BUT, because of our meddlesome selective breeding, you could also end up with lighter or darker shades.
In the case of platinums, theyw ere selectively bred from golds. The 'pale gold/brown' described (I think by Miss Dib Dabs) is likely related to someone's selective breeding experiments somewhere along the line to produce platinums. Again, these fish are probably descended from wild golds (for the most part) and, if crossed with blues, are likely to result in 'wild-color' fry. The selective breeding that went into producing lighter and darker shades of the various colors also probably played with polygenes. As such, you can get all sorts of different shades within one batch - even if the parents are exactly the same shade. Having said that, a very light shade X a very light shade probably would still result in very light fry so platinums crossed with platinums should produce platinums (but it all depends on the way these particular polygenes work and those I have any reliable knowledge of are limmited to cats' eye colors - another example, which I don't know much about, however, is human skin color).
Lavenders I'm not too sure about. They are supposedly the result of a gold X blue/blue opaline cross but I'm starting to have doubts as this would imply the blue is semi-dominant or, somehow else, the two colors manage to show up at once. I'm going to try to work that one out as soon as I have the time (I want to cross a couple of lavenders and see what I get - I actualy saw some at Pets At Home the other day! All covered in ich though
It's such a shame.)
Anyway, having profoundly confused everyone even more than necessary and having over-simplified things to the point at which, to me anyway, the stuff I've been saying makes limmited sense, I still think that, if any of this offers any insight whatsoever, it was worth it
The point, realy, is, regardless of what you are breeding to what, you can't predict what the fry will look like without more info. and still be 100% accurate. Can't wait for someone to map the three-spot genome (wishful thinking!)