Often times when opening your third eye chakra you can experience Intense dots of color that often range from blue, purple, green & white.
Upon relaxing and closing my eyes, I tend to get images in my minds eye. This feels much like dreaming when awake. Most of these images do not make any sense and can range from vivid to murky.
Depending on how high the vibration your operating at theirs dimensions that you can be able to pick up on. The higher vibration you operate the higher developed worlds you will be able to explore using methods like astral projection.
If you work at a high vibration you can see very vivid light & color as the general scope of what you see and the places you visit they tend to be golden or white.
Though at lower vibrations you will sometimes encounter demons or lost souls who of people who killed themselves but could not move on. Though I have seen lower dimensions as well. If you are prone to negative thinking you may not wish you open your Third eye.
General rule of thumb if you are feeling good you are having good thoughts, if you are feeling bad you are not. Keep this in mind prier to opening.
After mine opened I become more sensitive energies of people both good and bad. It offers heightened empathy but can also be overbearing at times for those already empathetic I can become drained after spending a short time populated areas due to the negative energy that most people carry on them!
I see flashes of color and see or sometimes feel other beings, when I close my eyes I will see as if I where dreaming images and as I progressed I have found many uses for this ability such as heightened clairvoyance and empathy. Though its not always rosy as for me at least when depressed I can get some very spooky images can come to mind. Overall, its worth it.
All the best,