Uniformity of (V-Near-Infrared) Color Evolution of Type Ia Supernovae and Implications for Host Galaxy Extinction Determination

From an analysis of SNe 1972E, 1980N, 1981B, 1981D, 1983R, 1998bu, 1999cl, and 1999cp, we find that the intrinsic V-K colors of Type Ia SNe of typical luminosity (i.e., with multicolor light-curve shape (MLCS) parameter -0.4<~Δ<~+0.2 mag) suggest a uniform color curve. V-K colors become bluer linearly with time from roughly one week before B-band maximum until one week after maximum, after which they redden linearly until four weeks after maximum. V-H colors exhibit very similar color evolution. V-J colors exhibit slightly more complex evolution, with greater scatter. The existence of V-near-infrared (NIR) color relations allows the construction of near-infrared light-curve templates that are an improvement on those of Elias et al. from 1985. We provide optical BVRI and infrared JHK photometry of the Type Ia supernovae 1999aa, 1999cl, and 1999cp. SN 1999aa is an overluminous ``slow decliner'' (with Δ=-0.47 mag). SN 1999cp is a moderately bright SN unreddened in its host. SN 1999cl is extremely reddened in its host. The V-NIR colors of SN 1999cl yield A_V=2.01+/-0.11 mag. This leads to a distance for its host galaxy (M88) in agreement with other distance measurements for members of the Virgo Cluster.