Yosef Chayim, Ben Ish Chai: Halakhot: Hilkhot Chanukah
“ Make the lamps the same; good for shamash to be different יג Do not light some lamps of oil and some of wax, in order that people not say that two people lit, and also this is not an enhancement of the mitzvah, therefore it is good that the bodies of the lamps too be equal in size, appearance and type, for the sake of enhancing the mitzvah. And it is good that the additional lamp which we call the shamash should be made differently than the Chanukah lamps, in order that it be recognizable that this is not included in the Chanukah lamps, and this is what I do. ”
