Colouring dried flowers

We flattened and started to dry a few flowers that our daughter received at her graduation.

Red flowers. They are turning brown. This is something that happens. We dipped them in vinegar (as suggested online), but the petals are turing brown.

Is there a way to dye them back to red? We thought we might be able to even artsy them up and paint the petals with acrylic paint.

Does anyone have experience or advice to offer?

Thank you.