The shade is described as a white with a lilac flash and the finish is Frost. It is duochrome and appears white in the pan, but once it is applied on the lid, it can appear white, blue, or lilac. It can be used as a highlighter, liner, or over other shades to transform the overall look. The first step I took in the search was to search the MAC website and see what they had to say about a replacement for this shade. They suggested one shade that might be considered similar, White Frost. This shade is a frosty vivid white with an icy shimmer. However, it does not contain the duochrome, making it unacceptable as a dupe for Vellum.
I began my next search at Sephora, the odds there are pretty good that I will find something close. In the Bare Escentuals area, I found a shade in their Glimpse Shadow collection called Flamenco, which is a bright lavender. However, it doesn't have quite the same frosty finish and it has no duochrome so this one is a no-go.
Next, I went over to Urban Decay. Personally, I find the quality of Urban Decay's shadows to be a higher quality than that of MAC and have been a favorite of mine for quite a long time. I found several shades that are possible contenders in this area. The first shade is called Asphyxia which is a lavender with a blue sheen. First thought - Yes! A duochrome! However, I kept looking at other shades to make sure that I can find the closest dupe on the market. I looked Grifter, which is a sparkling pale purple. I also looked at Stalker, which is an intense lilac with silver glitter. Then I looked at Flash, which is a bright violet sheen. After this round, I decided that Grifter is a bit too pink to make the match and that Stalker and Flash are both a bit too dark.
At the Lancome counter, I found a shade called Color du Jour. This is a very pretty lilac but it not shimmery enough to be a dupe. Also, it has nothing that resembles the duochrome. I am just storing this color in the back of my brain because I think that I will be wanting this one for myself in the coming months.
At this point, I am thinking that Urban Decay's Asphyxia will be the winner but I wanted to check the NARS counter out because I am also quite a fan of their eye shadow formulation. The only shade that I found over here that is even close is Night Rider, one of the pale shades in the famed Night collection. This shade is described as soft plum with silver glitter but I think that it is a bit too dark to be an accurate dupe. I also looked in the Cream Shadow area but to no avail, there was nothing that would even be a close dupe to the original.
So the winner is Urban Decay's Asphyxia because it a lilac that has the duochrome quality to it so it can also flash blue. This is the only shade with the duochrome and therefore, the only dupe that I could find.
photo courtesy of Sephora