@andesheng No problem, I’m glad we could help! I’ll separate my answer in three parts to try to answer your question thoroughly:
1) Please visit the following post in the FAQ live thread, as I’ve answered a similar question regarding how to change the onion skin transparency between frames:
[Updated link] Pencil 2D FAQ (now open)
It’s a detailed explanation (images included) on how to activate the onion skin through multiple means as well as where you can access the transparency properties for previous and next frames, which to me seems in part what you’re asking.
2) I’ll have you know as well that the white background in pencil2D is not actually white, in reality it is only transparent and the color is just for visualization purposes. So I would recommend you to either import a color background or create one inside pencil in a different layer.
If you need to, you can change how to visualize the default Pencil2D background by going to Edit > Preferences > General > Background > Choose one of the radial button options and you will see the canvas “transparency” change in real time.
- The third thing that you might need to know is that Pencil2D has a system that handles relative visibility beween layers. Here’s a short video you can see to clarify this point. It was a bit rushed because I didn’t have much time to record, but I hope you understand the concept.
Hope all of this helps to clarify your initial question.