Morning! I want to put gumpaste flowers on a Chocolate buttercream frosting. Do I need to worry about the grease from the buttercream discoloring or softening the dried gumpaste flowers. Thanks for your responses.

i have never had an issue. Once the gumpaste is truly dry, you should be fine. but - I wouldn't put the flowers on until the icing on the cake has had sufficient time to set up.

Thank you for your help. This is my first big show of a cake, non family/friends. Nervous.

Depending on the flowers used it *may* have a problem but for the most part no.
Did you make the flowers or are they purchases?
If you have an extra one or two just spread some icing on a plate and set the flowers on it for a day and see what happens.