When it was brought up a bit ago, I thought I was aphantasic. It turned out I'm just poorly trained at it - I don't tend to rely on memory for physical details, and I'm aggressively poor at visual arts. With a little thought put into it, though, I realized I can "See" in my "Minds Eye", and with some active training I'm still not good at it - It's not a tool I reach for naturally - but I can "Imagine" some images if I try at it.
Look at something. Close your eyes. Retain the image. Try to "look" at parts of the image. Focus on parts of the image. Then... change them. No, that apple was green, not red. You know what a red apple looks like, you know what a green apple looks like; Focus on the overall feel of the rest of the image while the apple is different.
It's not easy, it's a trained skill, though I guess one that's pretty easy to acquire accidentally by daydreaming and doing art. I think I actually trained myself out of it as part of "safety" training; I stopped relying on mental models of many things and started forming mental models of the checklists to get them into that state.
