Straps can be a problem. Even though many costumes and undergarments come with adjustable straps now, they aren't really invisible. The clear plastic straps look shiny on stage and break easily, the "nude" straps don't seem to match anyone's skin tones. Solution? Make your own invisible straps.
1. Take the clear plastic straps that you want to replace and remove the fittings from them.
2. Cut a piece of regular elastic a little shorter than clear elastic (this is because the clear elastic stretches less than other elastics). White or unbleached works well for this. For best results, find elastic that is the same width as the ones you are replacing.
3. Attach one of the hooks to the end of the elastic and sew the hook in place.
4. Slide the fitting that does't have a hook end onto the other end of the elastic so that the bar side is on top of the elastic on the wrong side of the strap.
5. Slide the 2nd hook on the end of the elastic - make sure the hook is facing the same way as the one you sewed in the beginning.
6. Loop the elastic over the bottom of this fitting and thread it back through the bar fitting you attached in the last step.
7. Fold the edge over the bar and stitch in place.
8. Take a cream or liquid foundation in a color that matches your skin tone and sponge it onto the strap. Put the strap on your garment, adjust to the proper length and make sure all of the exposed elastic has a coating of foundation on it and your straps will be invisible from stage. For best results, remove the straps before cleaning your costume.