This little exercise illustrates why you cannot always paint white objects white. In order to get the effect of brilliance that a flame produces, you need to mute everything else.
Candle flames are much brighter than white paint, which is the lightest value a painter has at his or her disposal. Therefore, this candle is more of a middle tone than a light tone.
The "white" tulip is also a middle value. It probably would have been even more effective if I had used a darker background and an even darker value for the candle, but since I wanted to use this color for the background, I had to compromise a bit.