What ever happened to those classic plastic birthday candle holders, the flower-shaped ones? Why don't the local grocers carry them any more? A Google search uncovers some, and while some of them appear to be NOS, others appear to be new.
Thankfully, I have a large assortment of them around the house, as I don't regard dyed paraffin wax as "Good Eats."
We have a family tradition of using white candles for decades, and colored candles for single years. We haven't yet had a need to reserve a color for a centuries digit. For example, 7 white and 7 blue candles on my dad's 77th birthday cake:poundcake.small
, on Flickr
(and note the white candles in blue holders, and blue candles in white holders)
At any rate, the logical thing to do is to find out what sort of candles the customer wants
to put on the cake, and how many, and incorporate that into the design.