Well, one risk is that you may not get the color you’re expecting. To the good side, though, green or purple or blue hair is not as unusual as it used to be. You can always pretend that’s what you meant to do.
I was a honey blonde from childhood into my twenties. Once while in college, just for fun, I did my hair dark brown. It was kind of a kick. The most startling thing was how dramatically different I looked to myself. I’d glimpse my image when passing a mirror and halt because my peripheral vision had detected a stranger in my vicinity. Really, it was shocking to me.
I think that was mostly because it drastically changed the degree of contrast between my flesh tones and my hair color. Fair-complected blondes have a much lower contrast than fair-complected brunettes. Darker hair just frames your features differently.
After a bit the brown pretty much wore off, and I never did it again. Now I use coloring products to try to keep my natural color, not cover it.
I’d say maybe use a temporary rinse just to see how it feels, or go try on some wigs. You can probably learn enough in the first few minutes to satisfy your curiosity.