I have been thinking about casting my very first circle I have almost everything I need. I got my candles a couple years ago, yellow, blue, green, red, and purple to symbolize the elements. And yesterday I dropped one and a piece chipped off and underneath it was white and it got me to thinking. Would I need to use candles that are a solid color or would candles coated in that color with white underneath work?
The colors are merely of symbolic value, nothing more. Candles are used for stimulating emotion and inspiring one to feel what they're casting.
Some people don't even use colored candles, some carve sigils into them and that works for them just fine.
The idea is just go with what you feel necessary and what you're comfortable with. Candle magic or using candles in magic is not a rigid practice, so if the white candles with colored coating works for you then they'll work for the circle casting. If you prefer solid colors then by all means, use the solid the ones instead.