See question above. Dear Rov I wonder did you not once wrote that one should avoid using flame-lights of different colors, so why is this case different.

Indeed on question 684 we addressed the following Shaila: “Dear Rabbi, I teach sciences in a frum school. I was teaching about the way you can create a variety of colors in flames by adding different chemicals to the fuel. One of my students was wondering if you are permitted to add them to the oil or the candles of Chanuka. Since the effect is quite attractive and striking, would this be a hidur mitzvah or a greater persumei ness?” To what we answered: “Remah (O.H. 673: 1) rules that one should light preferably with olive oil. Mishna Berura (ibid. 4) quotes Mahari Brin (or Bruna) and the Maharal, and explains that the reason is since the miracle of Chanuka occurred with the traditional olive oil used in the menorah of the Bais Hamikdosh, the mitzvah of lighting the candles should resemble the original as much as possible. Eliahu Rabbah (ibid. 2) maintains that this applies even when the olive oil is costly, although other Poskim disagree. Therefore Horav Shlomo Miller’s Shlit”a opinion is that although the lighting would be acceptable if the flame coloring additives mentioned were to be added, it is preferable to use the most pure olive oil available.” However, in our case it is a single color variation that is common to many metal Menoras.