I can visualize the ball without color, so while having aphantasia implies no color, the converse is not true. It's sort of like an autostereogram, but with only the depth effect and no color at all.
Aphantasia doesn't lack color, it lacks a place to put the color and therefore color has no relevance other than descriptive. The ball is just an imaginary object, like an uninitialized variable. I can imagine that one exists, I can imagine that it would have traits like red or blue, big or small, bouncy or not, but I don't visualize it, and those fields need to be filled in one-by-one, they aren't defaulted when I imagine a ball, and nothing changes other than the description if I change them. A ball rolling off a table is more like the lead into a physics question to me than an exercise in imagination.
> The ball is just an imaginary object, like an uninitialized variable.
As someone who has been coding for 45 years, this is absolutely the best analogy describing aphantasia I've ever read. Obviously, it works only when talking to another coder, but that is better than nothing.
Right now I can only visualise with a colour… unless "transparent" counts as "without". But even then, there's a full-colour environment for the transparency to be meaningful, and it can't be total transparency because then it isn't present. Even if I imagine a wireframe grid to show where it is, the grid has a colour.
What if I asked you to visualize a wogembibobble rolling off a table, would you be able to visualize it, and if so would you say it has a color? And if you're curious what a wogembibobble is, all that you need to know is precisely what can be inferred from the question: it's something that's cabable of rolling, and all other variables are free. When I do this exercise, I visualize a bulbous-tentacled blobby sort of slime rolling off the table, but although I can't imagine it without giving it a shape (and even a texture, apparently), I can imagine it without giving it a color. I don't pretend to know how this works, and I assume other people will have different experiences.
I imagined something about the size of a duck made up of hundreds of little brass pistons and cam shafts, and as all the little pieces move it makes the whole thing move sort of like an amoeba. So when it rolls off the table it’s kind of like if you rolled a blob of mercury off a table - but it rolls itself, and there’s more clicky clockwork sounds.
FWIW, @a_cardboard_box's description doesn't sound like anything I personally experience.
Not that we should expect immediate agreement on any of these things: words can only gain meaning by shared experience, and it's really hard to share the experiences that are confined to the inside our own skulls.