I used to preserve diseased plant parts and keep the colors of the infected plant parts intact.

The method is as follows:-

I part of Copper sulphate crystals to 4 parts of glacial acetic acid (by weight) and then dilute the solution 20 times. Boil the plant part or parts in the

diluted solution and then dry between newspapers. All the colors will be be preserved. Air the parts frequently (to remove the vinegar smell) and keep

putting them between fresh newspapers (to remove moisture) and retain the shape.