  In this paper, we consider the colorful $k$-center problem, which is a
generalization of the well-known $k$-center problem. Here, we are given red and
blue points in a metric space, and a coverage requirement for each color. The
goal is to find the smallest radius $\rho$, such that with $k$ balls of radius
$\rho$, the desired number of points of each color can be covered. We obtain a
constant approximation for this problem in the Euclidean plane. We obtain this
result by combining a "pseudo-approximation" algorithm that works in any metric
space, and an approximation algorithm that works for a special class of
instances in the plane. The latter algorithm uses a novel connection to a
certain matching problem in graphs.
