I would use a product called Retro Clean, that is available in quilt stores or through Amazon. I used it on a linen table scarf that I purchased from an antique store. It was embroidered on a pale yellow linen with taupe crochet on the edges. It is a soak so not harmful to stitches or fabric etc. The table scarf came out sparkling white with pale blue crochet! Turns out the scarf must have been exposed to cigarette smoke over the years. The embroidery wasn't affected but brought out the brilliant colors. I was amazed.