RTK - it shouldn't be your job to know anything, they should tell you what's available! Meanwhile back at the NHS, they probably assume if you wanted open fit but had to get moulds, you'd want the moulds as invisible as possible so are making standard transparent ones. 95% of people getting hearing aids are over 65 and apparently they all want everything tiny and 'discreet' and as few options as possible, which is why so many aids don't have obvious things like on/off buttons or volume controls. (insert long rant here...)
Try calling them on Monday and saying if you have to have moulds you'd like them in whatever colour (red, pink, blue seem to work) and with glitter. Worst that can happen is they'll say they only do it for under-18s. And you may get the wrong colour - I was after dark purple but gave up...
Shouldn't take any longer, they just add a dye when making the mould. The tubing only comes in clear as far as I know, and the aids come in a variety of colours but possibly only red, blue, green and yellow - many don't come in black. But transparent shows off the gold contacts inside so it's quite cool. Again, ask. You can also buy funky animal covers to decorate the aids, for about £15 online.
I don't wear glasses but apparently modern aids and thin glasses frames should be fine after a few days.
Good luck with it all, and don't be afraid to go back as often as necessary to make sure the aids work for you. The audiologists get bored of all the standard settings for the elderly people who won't give any feedback at all!