Hey bro, You make trees look really posh!
An idea perhaps, try using the HSB sliders too, if you haven't already, RGB's are nice but HSB's are also nice. =)
Also I notice you block in with opacity.. maybe lay your first value down at 100%, like an average grey or something, anyway, it's just an idea, you have your methods, I wouldn't like to mess with them.
Keep up the fantastic works and looking forward to your nexts. =)