This thread reminds me of an anecdote. A few years ago, I had the opportunity to join a one week "qigong seminar" animated by a wandering student of the Chinese qigong master Wang L#ping. Most participants were students of Chinese Traditional Medecine, half of whom were studying acupuncture in the hope of quiting their jobs and starting a new life in the well being industry.
Before describing what happened during this seminar, let me first remind everybody of what "qigong" is about. Qigong is a Chinese practice aiming at "circulating" your body's energy ("Qi") in order to enhance your health or to become an "immortal" / a "fairy" (both words being a very poor translation of the chinese word xian (仙) designating transcendent beings). I won't delve into the (im)possibility of attaining this goal (it didn't work for me !). Neither will I attempt to discuss what "qi" could or could not be, or even if such a thing exists at all. Let's just say that qigong stands somewhere between health practice and religion. As Charles Luk once implied in its translation of Zhao Bichen's works, it is very much a kind of Chinese "Yoga". There are no "cakras" in qigong, but there are acupuncture points and channels.
Now, going back to my little experiment : in this qigong seminar, after lecturing us for while on taoist religion, our teacher led several meditation sessions using various breathing and visualisation techniques. It was interesting in itself. But what was even more interesting was that some other participants did envision weird and spectacular things during the process. One lady had a vision of a dragon and a tiger appearing in her mind while meditating ! And she was quite amazed by that. She felt great relief to "at last have found the "master" she had waited for all of her lifetime". Yes, she felt she was the "chosen one" ... Anyway, observing her, I noticed that it was enough for her to hear the Chinese teacher's voice to instantly enter a kind of trance. In other words, she was obviously very open to suggestion. And suggestion induced her to do and see bizarre things.
So I think that it is not unusual at all to have visions while doing yogic activities. If you expect things to happen in your mind, your mind will probably grant you your wish. For instance, if you crave for a cheeseburger, you may behold the advent of The Holy Shining Burger from Beyond !
According to various authorities in Eastern religions, it is something to be expected if you spend much time meditating. They do not necessarily claim that it is the fruit of auto-suggestion, though, but most of the time mystics are advised NOT TO focus on weird visual phenomena, and to let them go when they occur.
A taoist priest of mount Baima, in northern Hubei, I once had the chance to meet, wrote a "summary" of his practices emphasizing that high level adepts at some point inevitably witness grand visions of lights and "spirits" (neither whisky nor vodka, though), but if they dwell on contemplating these visions they end up being diverted from their goal.
In some traditions like Tibetan Buddhism and Bon (native tibetan religion), it seems these vision have even been given a religious explanation (theory). If you are interested in this, I recommend Loel Guinness's book on the "rainbow body". To sum up what I've understood from this book, the Bon yogis think that intensive meditation enables them to envision the "basis" of consciousness by cleaning up whatever obstructions prevent us from seeing our fundamental "nature". According to them, this inner "cleansing" process opens some channels within the body, and one of these channels links the heart to the eyes. Therefore when a yogi reaches enlightenment, this channel being cleansed of all obstructions, he will begin to physically experience various visual phenomena, as the "light" from within supposedly shines forth to his own eyes. At least that's how they explain visual phenomena in this religious tradition. It appears that yogis from this tradition see rainbows and colourful mandalas. Still, they must recognize that these are just projections of the mind.
Therefore, I would say that seing violet, red, blue or yellow clouds during a meditation should not be surprising. Neither would an apparition of the Virgin Mary, Lord Rama or the Buddha.
The great question is : what does this tells about us ?
And since I am neither a great neuro-scientist nor a a great yogi, I am in no position to answer ... So sorry for wasting your time with this post.
