Not all candles burn the same colors. You should keep your candles in dry places. If it is a devotional candle and flashes, it means that you have contact with the deity and the request must be heard every hour. It can cause all sorts of problems like soot, growth tunnels, and more.
If the glass breaks or breaks, it means that you bought a candle in a holder that should not withstand the heat of a burning candle until it goes out. When a candle is lit, there may be popping noises.