  The recent discovery of microlensing of stars in the Large Magellanic Cloud
has excited much interest in the nature of the lensing population. Detailed
analyses indicate that the mass of these objects ranges from 0.3-0.8 solar
masses, suggesting that they might be white dwarfs, the faint remnants of
stellar evolution. The confirmation of such an hypothesis would yield profound
insights into the early history of our galaxy and the early generations of
stars in the universe. Previous attempts have been made to place theoretical
constraints on this scenario, but were unduly pessimistic because they relied
on inadequate evolutionary models. Here we present the first results from
detailed evolutionary models appropriate for the study of white dwarfs of truly
cosmological vintage. We find that the commonly held notion that old white
dwarfs are red to hold only for helium atmosphere dwarfs and that hydrogen
atmosphere dwarfs will be blue, with colours similar to those of the faint
point sources found in the Hubble Deep Field. Thus, any direct observational
search for the microlensing population should search for faint blue objects
rather than faint red ones.
