It is ritual, ceremonial, and it is symbolic in nature as a tribute and recognition, a piety. Because red, blue and black are the colors of Satan and this goes back as far as the days of Ancient Egypt, which was known as the Black and Red Earth and was the abode of Spiritual Alchemy. In turn, Spiritual Alchemy is known as the Path from Blackness to Redness. It is interrelated and has allegorical overtones.
While the above is significant, in terms of the depth of understanding of the meaning of the colors themselves and what they represent, it is not an absolute rule that must be followed for Initiation. You may choose any candle you wish, but the only important thing is that it must not be a church-made candle, otherwise it is sacrilege.
Everything else comes from how you feel and what your intentions are. Zeus/Satanas is infinitely merciful towards his children and equally infinitely understanding, he sees through you, so it is more important what you have inside, not how imposing and pompous you make the Rite/Ritual. Initiation can be done even in the Astral Temple if you can. So don't worry.