You can do as you will, but honestly, why are you casting a circle to meditate?

Edit: Okay. That’s not a reason to do a circle. Seriously. Circle doesn’t “keep out.” It’s a common mistake, based on confusing the “Casting the Circle” (Erecting the temple) with a summoner’s circle.

Try doing the meditation focused completely within yourself, not upon the ephemera.

yeah, you can do both. Spellcrafting, in a sense, is a form of meditation, as you are projecting an intention into the astral plane.
Elememtal water is to the west. I use blue candles for Water representation, though I know some pagans who use green, silver, and white. You don’t HAVE to have candles representing the quarters– it all depends on what you believe, and if you feel it makes your craftworkings more powerful or not.
Again, the outcome is all entailed by what you believe.

I sometimes use different aids for meditation: nature sounds CD’s, water fountain, candles, incense, drumming, and sometimes nothing but just me in a quiet space. Whatever helps you, you can certainly use it. If you want to use a candle with color correspondence, I would go with purple which is associated with the third eye chakra, spirituality, and psychic development, since this is the area you’re working with when meditating.

Agreed with LabGrrl on the circle casting part. You can simply cleanse your meditation space, I smudge the room before meditating in it to cast out any negative or unwanted energies. Or you can put up a “psychic shield” around yourself before you enter into meditation.