Hi, I'm planning to have Issue 3 of Peregrine focus on a bit of his backstory (on his experiences at the Attica School for Anomalies), and I was wondering about any tips and tricks there are to drawing flashbacks, apart from changing character's appearances a bit.
One idea I had was putting it in grayscale, like the background in this panel:
However, I was concerned that it would detract any new readers.
If you want to keep the colors then another option is to feather the borders of the panels that are part of the flashback. A white or grey feathering effect, like the ones you see in some wedding and graduation photos, would pick out the flashback panels from the main story without changing the overall style.