The VT will override the Delta, the VT may be a bit wider at base, but otherwise you will get only VT.
For colors it will be a hodgepodge.. all depends on their parents and grandparents. Most likely you'll get a fair amount of blues with red wash, reds.. basically a grab bag full of reds, blues with clear and whitish fins, etc.
Before you breed them, think about where you will find homes for them.. sadly, neither of those fish are breed worthy to be completely honest. They aren't ideal specimens for either fin type they represent.. and with them being VTs you will most likely only be able to find homes for them local as most people will rather spend all the money it costs shipping a fish on a fish that is a bit more "flashy", and not one they can pick up at Walmart for a few dollars. So consider how you will be able to sell 100+ VTs before you breed them. Good luck!