I too have some weird thing going on with the color purple. I remember in every shroom trip I have had the most dominant color I see around me is purple. And now with HPPD its still stuck with me. When I'm in a dark setting and close my eyes I get very intense closed eye visuals (CEV). And in these CEVs that I get the only color I notice is purple. a very rich deep beautiful purple. And I'm sure you are aware of these 'after images' most people get with HPPD, and most of these 'after images' I personally get are a form of purple.