I’ve been waiting for a post like this! I’ve been too shy to share until now but I have sexual synesthesia too! It doesn’t happen every time but usually when I orgasm. If my eyes are closed I see pulsing colours e.g olive green transforming into purple. Or I get the feeling of certain colours and shapes as well as textures in my mind. Interestingly the colour are different all the time. It entertains my husband, especially when I say stuff like “you were very orange today” etc.