I recently took on this project. I made some nice motoroil stix. They were almost the same as Berkeley's motoroil. The only problem is that they changed colors after a week or so. They no longer have a chart. tint to them. Therefore, I think it can be done, but you'll have to find the right dyes to do it.
Out of curiosity, what formula did you use??? I used a combination of Del's motoroil and LC amber. I don't remember the ratio between the two off the top of my head (I have it written in my formula book at home). I do know that I used a lot of motoroil and very little amber (I think 15 drops of MO and 3 or 4 amber).
Also, I use salt and sugar flakes (from senkosam) to get the weight for my stix.
Eric