I have never done this however I think this will answer your question. www.todayshomeowner.com/how-to-paint-over-ceramic-tile...
I did it 20 years ago, worked very well with epoxy spray paint, Prep was critical and ventilation and curing time. I am sure there are many new products and videos out there now. But I probably have 30 lung diseases from the fumes.
I painted the tile in my shower area many years ago and eventually the paint began to peel. The tile paint products that are currently on the market were not available at the time that I painted my tile. I used a high gloss paint and several coats of polyurethane and would not recommend this method. I plan to redo the area with one of the products that have been specifically designed for shower tiles.
I have painted ceramic tiles and would NEVER do it again. I researched it and used the best products and procedures I could find. It did last for a year or so but it looked like painted ceramic tile. I was very apprehensive to clean it with anything but very mild liquid soap and a very very soft sponge. It was way too much work, couldn't be scrubbed and provided only minimally satisfactory results. Just my opinion.
I have never heard anyone that was happy with the long term outcome of painting ceramic tiles in their shower stall.
I just painted mine this week with the rust oleum two part epoxy. I love it but please learn from my mistake. Cover your shower head with a plastic bag so there is absolutely no moisture. Also, truly wait an hour or so after cleaning with TSP to make sure the tile is absolutely dry. My walls came out gorgeous with a hard as nails finish. Where a small leak got the floor wet, even though I thought I wiped it well, the remaining minuscule amount of moisture make the finish so gooey that I had to scrape that small section off, sand and redo it. The result is beautiful, buh buy 1980's pink and mint green, but I obviously cannot speak to its durability.
I painted mine years ago when I bought a condo with a lovely Pepto Bismol pink and baby blue bathroom. I couldn't afford a reno and couldn't live with it the way it was. I used Kilz primer followed by latex paint. I used a narrow paintbrush to paint the grout lines white. It lasted with no chips for about 5 years before I did my reno.
I had a friend many years ago who used marine paint for boats to paint his shower. From what I remember, he never had any problems with it (or at least none that he shared!)
I painted mine some time ago using drylock