Whoa; chill! Nobody’s trying to take away your pink-beige hearing aids. And while I don’t actually know that much about the fabrication of plastics, my guess is that making different colours available is a teentsy-tiny expense compared to the cost of the hearing aid.
And in so far as we are giving credit to the marketing and sales machinery that drive the industry, my guess is also that they offer these choices because they do sell. Not to you, obvs, but to some of us. Check out the sales literature for pediatric hearing aids – intriguing, fun colours figure prominently. So they’re not just doing it – my guess, anyway! – because they read this forum and realize there are a few weirdos who want, whatever, hot-pink paisley hearing aids. As well, every hearing aid I have had has easily-removeable and -switchable outer shells. Takes a minute, in the office. It’s not like they have to retool the assembly line or anything.