Given a set S of n points in IR^D, D \ge 2. Each point p \in S is assigned acolor c(p) chosen from a fixed color set. The All-Nearest-Foreign-Neighbors Problem (ANFNP) is to find for each point p \in S its nearest foreign neighbors, i.e. the set of all points in S\{p} that are closest to p among the points in S with a color different from c(p). We introduce the Well Separated Color Decomposition (WSCD) which gives an optimal O(log n) parallel algorithm to solve the ANFNP, for fixed dimension D \ge 2 and fixed L^t-metric d_t, 1 \le t \le \infty. The WSCD is based upon the Well Separated Pair Decomposition ([5]). The ANFNP finds extensive applications in VLSI design and verification ([11]) for two dimensions, and in traffic-control systems and Geographic Information Systems (GIS) ([7, 12, 13, 14, 15]) for D > 2 dimensions. To the best of our knowledge, this is the only known optimal parallel algorithm for the ANFNP.