wow!, could you elaborate more on the technique, and what exactly happens?
just press on most of your eyes mostly except the bottom(or press on all of it, that works too) you can use the palms of your hands or the outer sides of your index fingers. Press just hard enough so it doesn’t hurt (it’s not good if it hurts!) you should see checkerboard patterns, and possibly a checkerboard tunnel also. After that you will either see some kind of 3d landscape or a yellow ring (if you don’t see it now you will see it later) do not focus on the ring but look at it. do not move your eyes in any way! eventually the large ring will come into focus as several animals or runes. And thats the end! I AM NOT LYING, If it doesn’t work for you that doesn’t mean I am. I’m still not sure if it works for anyone except me but i hope it works for you! 
could this possibly be unhealthy for your eyes?
a more traditional way is to look at a candle or a light then close your eyes and try to hold onto the afterimages
just once your eyes adjust to the dark, if you keep them open for a while then close them it can give you strong colors too.
when i was a kid i’d press on my eyelids and feel like i was flying though, but it was always black and white, so maybe it is a natural thrid eye development technique, or something.
it just doesn’t seem like it’d be good for you at all to put pressure on your eyes, that can cause glaucoma and stuff can’t it? I don’t know.
I did that for a minute just touching my eyes and I saw weird shapes in the dark. Also, once I was closing my eyes and focusing on the blackness and many images of eyes came to me, and when I went to touch my forehead it followed my hand.