I've never found any hint of such a policy. The redlining maps are from the 1930s, not the postwar era, and there's little evidence that lenders ever paid much attention to them. Not only were the maps not widely distributed, but Kenneth Jackson notes in Crabgrass Frontier that FHA and VA loan guarantees were only of modest important to postwar production homebuilders, used for less than a quarter of single-family units in Fairfax Co., Virginia, for instance. And racial stability was only one part of the “adverse influences” factor, which altogether was only 20 percent of the FHA underwriting guideline formula.

A 2002 journal article by K. Tobin called "The Reduction of Urban Vulnerability: Revisiting 1950s American Suburbanization as Civil Defence," in Cold War History, 2:2, 1-32 tries to equate some magazine articles (some by science fiction writers) ruminating about the possibility of decentralization with a federal decentralization policy. Her thesis is that some people tangentially attached to federal policy were talking about decentralization, and some decentralization happened, therefore it must have been deliberate. This ignores the rather prominent fact that the federal government plays no rôle whatsoever in the location decisions made by individuals, companies, or local governments. It's telling that she cannot cite a single federal law or regulation aimed at decentralization.