Organic resin compositions of from about 30 to 90 weight percent of a polyol(allyl carbonate), e.g., diethylene glycol bis(allyl carbonate), and from about 10 to 70, e.g., 10 to 30, weight percent of a mixture of aliphatic urethanes, the terminal portions of which contain allyl or acrylyl functional groups. Polymerizable compositions prepared from such compositions produce castings which have low yellowness (b*) values and which do not pre-release from the molds in which they are formed. Polymerizates prepared from such compositions may be used to prepare photochromic articles, e.g., lenses, by incorporating a photochromic substance, e.g., by thermal transfer, into the polymerizate.