Well, you don't have to be having sex with a guy to see his cock. Don't even need that to see his hard cock.
You just have to enjoy or be willing to be present when men are going to be present, naked, and possibly aroused.
Which is a long way of saying that I rarely have had sex with men, I don't enjoy it. But I've seen a lot of cocks, aroused or otherwise.
I was a nurse for a long time, and I enjoy group sex and orgies, as well as group bdsm.
Yes, some of them can be quite surprising. All kinds of sizes, angles, and colors. They can bend into very unusual arcs as well.
There was a gentleman at a party that was fairly long, fairly narrow, but it bent three times, almost into an § shape, like a double S. He called it his literal trouser snake.
There's all kinds of colors that can surprise you until you learn that they can happen. Very bright blues and purples for sure, but also greens and oranges. It isn't going to be an all-over coloration most of the time; the majority is going to be shades of brown to pale colors. But I have seen a few cocks that were a dusky purplish blue on the shaft, building to blues and purples on the head. It's all about the combination of melanin and blood under the surface to make the light refract and reflect in interesting ways.
They can be very lumpy sometimes as well. Football (american type) shaped is not super rare, and having bulges is common enough that it ceases to be startling after a while.
Oh, absolutely a demand.
The problem is that it's a very complicated thing, and that means you can't just gonna someone willing, they have to have the experience and skill as well, or it's going to end up bad.
It really isn't something most doms are into as their own kink. Picking up the "tricks if the trade" means having to spend your own time learning something instead of having fun for your own ends, if it isn't also your kink. That's as rare as finding a dom that has the kink tbh.
Back when I participated in the local scene, the feminization side of things was fairly rare, and not part of what most bdsm groups did when they met.
That being said, it can be fun to take part in, even if it isn't your kink. I have done scenes with sissies before, and while it isn't something I would want to do regularly, particularly if it involves sexual intercourse (be it oral or anal), even that is fine for the occasional bit of experimentation to get out of the comfort zone.
That's where most doms I've known stand on it. It's not their main focus because it really is a focus for a sissy. If you aren't doing that part of dominance, they tend to not be fulfilled by a session. It's kind of like pony play in that regard, you have to specialize in it to really get anything out of it long term.
But be patient. Be willing to communicate well with any potential dom so that there's no crossed wires. Doms that aren't used to the feminization genre of play can make mistakes that are easy to avoid if they're talked out in detail ahead of time. The few times I did it, I was lucky enough that the sissies I was playing with were very experienced and let me know what they needed rather than expecting me to magically know the ins and outs of it all. I know that breaks some of the immersion, but until you find a long term partner, that's the only way to go.
It comes down to the demand being much higher than the supply.