I had some vintage lavender beads that changed color to a light blue. Do you know what kind of bead they could be?
A jeweler would be your best resource as he could look at them in person and assess what material they are made from, and, if a gemstone material, what family they are in.
Based on your description, they could be glass or gemstone. Hold the beads--if they are gemstones they will warm to your touch; if they are glass they will stay cool. If a gemstone, it could be in the chrysoberyl family and possibly alexandrite. If glass, it could be an Alexandrite Swarovski crystal. Swarovski is known for creating color-shifting crystals depending on different light sources. The color seems to change but is really affected by the lighting in the room. Test out the beads in an incandescent light and then in natural light to see how your beads react.
Either way, your beads sound beautiful and fun to work into a design.