I also get these migraines with the visual sparkly colours. They start in the top left hand corner of my vision and work their way into my central vision and then eventually leave in the lower right hand corner. It is a half circle and usually jagged but not always.
The red dots and other visual disturbances people see are from pressure on the optic nerve caused by posterior vitreous humor movement. The vitreous humor is attached to the optic nerve so as we age it changes shapes or deteriorates and this causes visual disturbances such as the green dot/light, which I also get. I also get black flashes of light when I blink. It is all very stressful but degeneration of the vitreous humor does not cause any blindness.