I need to make the sky gradually start changing color half way through the scene. Initially I created three clips, one with blue sky one with red sky then pulled them into my video editing program and used a cross dissolve; then had the character on top in a green screen. That worked fine until I added FX to the character and the FX didn't show up on the green screen. So instead of three separate clips I need everything in one. That means changing the sky color within the scene. I tried pulling in a second sky to turn on and off but when I pulled in a new sky it deleted the first. I also want it to be gradual not immediately turning on and off.

Everyone has always been so helpful in my learning, I look forward to your advise. Thank you.