My preference for framing my hand torn deckled edged pastels is floating the art on an archival white mat to show off the gorgeous color filled edges. Then framed by another mat. I usually choose white for gallery and continuity purposes. The frame color itself depends on the colors in the piece of art. Here I have selected a gold frame to go with "Mediterranean Olives" for my art collector.
When you go to a professional framer this is what you see pictured here. Just one corner and you imagine the rest of the piece as it would be framed. You can try many sample ideas on all four corners if it helps you to envision the final piece. You can bring your camera and take a photo to better help you see your selections in a new perspective.
Pastels are artists' purest pigment. Pastels do not need to be retouched even after generations. Pastels DO need to be protected by glass. Your framer will suggest a few types of glass.
Here is a piece framed to completion.