I have not tried Custom Blend but I've considered it. I have dry, uber-sensitive skin with rosacea (so prone to redness but it's under good control at the moment) and have to be very careful with anything I put on my face...can't use any oils at all, bismuth, free propylene glycol, among other things. I recently tried Prescriptives Virtual Skin and really liked it. Shade-wise I just picked my own online as it was pretty obvious to me. It looked great and it didn't irritate my skin, at least after a couple tries. I still prefer my Alima MMU both for looks and ingredients, but it's always nice to have options. I was considering trying the Prescriptives Custom Blend more for getting rid of the chemical sunscreen in Virtual Skin than for color matching purposes because Ecru is a very good match for me, but then I would be getting talc which I'd also prefer to avoid. All in all, I'm quite happy with Virtual Skin for a liquid foundation. FYI, here are the ingredients for Virtual Skin and Level 1 Custom Blend base, as provided to me by Prescriptives consumer care:
VIRTUAL SKIN FOUNDATION:
ACTIVE INGREDIENT: OCTINOXATE 5.40%
INGREDIENTS: WATER (AQUA PURIFICATA) PURIFIED [] DIMETHICONE [] CYCLOPENTASILOXANE [] GLYCERYL STEARATE SE [] HDI/TRIMETHYLOL HEXYLLACTONE CROSSPOLYMER [] BUTYLENE GLYCOL [] TALC [] CHOLESTEROL [] TRITICUM VULGARE (WHEAT BRAN) EXTRACT [] MELANIN [] SODIUM HYALURONATE [] TOCOPHERYL ACETATE [] OLEA EUROPAEA (OLIVE) FRUIT EXTRACT [] POLYACRYLAMIDE [] PALMITIC ACID [] C13-14 ISOPARAFFIN [] LAURETH-7 [] LINOLEIC ACID [] PEG-9 DIMETHICONE [] CITRIC ACID [] SODIUM CITRATE [] DISODIUM EDTA [] SORBIC ACID [] IMIDAZOLIDINYL UREA [] PHENOXYETHANOL [] METHYLPARABEN [] [+/-(MAY CONTAIN) TITANIUM DIOXIDE (CI 77891) [] IRON OXIDES (CI 77491, CI 77492, CI 77499) [] MICA]
Custom Blended Foundation Level 1
Level 1 –
INGREDIENTS: WATER (AQUA PURIFICATA) PURIFIED [] DIMETHICONE [] BUTYLENE GLYCOL [] OCTYLDODECYL NEOPENTANOATE [] CYCLOPENTASILOXANE [] TEA-STEARATE [] GLYCERYL DISTEARATE [] TALC [] PHENYL TRIMETHICONE [] STEARETH-10 [] SILICA [] SODIUM HYALURONATE [] LECITHIN [] BISABOLOL [] CHOLESTEROL [] TOCOPHERYL LINOLEATE [] DIMETHICONOL [] TOCOPHERYL OLEATE [] MAGNESIUM ALUMINUM SILICATE [] TEA-ISOSTEARATE [] CELLULOSE GUM [] XANTHAN GUM [] DISODIUM EDTA [] BHT [] SORBIC ACID [] PHENOXYETHANOL [] METHYLPARABEN [] BUTYLPARABEN [] ISOPROPYLPARABEN [] ISOBUTYLPARABEN [] TITANIUM DIOXIDE (CI 77891) [] IRON OXIDES (CI 77491, CI 77492, CI 77499)
As you can see they both contain parabens, which is the ingredient side of why I prefer the MMU, but I don't think they are otherwise too bad for someone with sensitive skin. I think there are some informative reviews about Custom Blend and the process in Productville on MUA. HTH!