Sorry to say, that is completely normal. Afterimages are caused when the cells in your eyes receive too much of a certain color; they then stop sending that color’s signal to your brain for a while. A white surface amplifies this effect since white sends all colors of light into your eyes at once, and the colors you have adapted to are edited out, changing the appearance.
This test works in exactly the same way; using afterimages. No matter how you hold your hand, you will see the same effect on the wall. Other people will produce the same effect. While afterimages are interesting illusions, there is nothing remotely mystical about them. Sorry.
Hehe, auras are not the same as after-images. After some time, you begin to see colors and shapes in the aura that change and fluctuate with the person. One can manipulate the aura with certain practices, and this is a visible phenomena.
But you are right in the idea that there is nothing mystical about them.
Replaced a huge full post quote with @moonsong, please use quote sparingly.
Hello again I have done this several times now with objects, and I tested it with Vokteraven. He has a bluey kind of aura, when his body was against a white background.
Im guessing that different colours resemble different moods or personalities or something? xP
From what I know, blue means calm and content. But Im sure it has other meanings too
Many people have discussions as to what colors mean what, but I’d encourage you to observe people, and find your own conclusions. As you improve, the more color you will see in a single aura, and in different areas.
I’m glad you had success with this! I find it to be a very soothing and fascinating practice.
I have done this several times now with objects, and I tested it with Vokteraven. He has a bluey kind of aura, when his body was against a white background. 
