<<Artlandia`
TwoColorMap[fun_, dim_] :=
Show[Graphics[RasterArray[ArrayOf[{Red, Yellow}, dim,
GeneratingFunction -> fun]]], AspectRatio -> Automatic]
TwoColorMap[RandomArray, {50, 50}]
TwoColorMap[NaturalArray, {50, 50}]
TwoColorMap[RandomWalkArray, {50, 50}]