I've discovered to my great annoyance, that once I move a color gradient or some other complex style to a resource dictionary it is out of Expression Blend's Visual Studio WPF Designer Thingy's jurisdiction and must be edited in XAML. I have no issues with working in XAML except that it is more time intensive than a designer. So my question is simple. Are there any designers for resource dictionaries?
I'm a Silverlight guy so possibly my answer is not valid. However in Blend you should be able to design resource dictionaries just fine. Go to the Resources tab and it should list all the dictionaries in your project. Expand the one you are interested in and you can design all the resources inside from there.
https://i.sstatic.net/7Ph33.png
If the resource dictionary in question is not listed in the tab, open its file (double click it in the Projects explorer), then it should show up. I believe this is a bug in Blend (I'm using 4.0.20525.0)