Flux-constant, hydrostatic model stellar atmospheres have been calculated using effective temperatures, gravities, and abundances appropriate for Cepheid variable stars. These models have been used to compute synthetic spectra, which have been used to compute synthetic colors and the visual surface brightness parameter S(v). The Johnson system color (V-R)J has been found by transforming the Cousins system color (V-I)C, using new transformation equations. The Barnes-Evans method has been used to find distances for 23 Galactic Cepheids, using the synthetic colors and surface brightness to interpret observed colors and magnitudes and the observed radial velocity curves. The importance of changes in surface gravity and Doppler broadening velocity on the visual surface brightness and color relations is discussed. 93 refs.