Ding, we would appreciate some photos fo your work, maybe you are too hard on youself
For color please try the following steps which was mentioned in David's post before, unless you already did try it out.
The simplest method is to place the flower on a layer of dry white sand in a container. More sand sprinkled around the flower until it is covered, and it is then left for three days in a warm dry atmosphere. It can then be removed and sealed with polyurethane varnish or hair lacquer. Flowers sometimes tend to change colour, due to the dyes being affected by the resin.
Flower preserving chemicals for can be obtained from your local chemist. Stamps and other paper items should be sealed with a thin coat of polyurethane varnish and dried before embedding. Coins, etc., need no special treatment as long as they are clean and dry.