A certain moderator must have spotted me lurking around the forum again, and gave me a nudge about maybe posting some pics and info about some gum trees I've been modelling lately. Being an Aussie modeller, I can't get any more back to my roots than really having a go at modelling some of our iconic trees.
We recently had the Australasian NMRA Convention here in Melbourne, and I was there to present a couple of clinics on how I do these trees.
Also a couple of pics of how they have progressed.
Here's some of the initial builds...
A couple of the trees on one of my diorama's, which is a fairly close prototype build of a former small goods shed on a local former narrow gauge line...
The file may take a little while to download (10.41MB). Link worked ok when I just checked it (will give you a black/grey screen as the download starts. Let me know if you still have troubles and I'll email you a copy.
I was going to put in a few colour samples, but I tend to not stick to a strict formular (I gather you were refering to the foliage variations). I just add the yellow, and then the red to a visual liking. Some batches definately turn out more lighter or browner than others, but that all just contributes nicely to the overall colour variation.