buildTypes

In the productFlavors section, you can see the mapping between the signing configuration for the release of a particular flavor and the entry in the signingConfigs section, which we examine after the buildTypes section:

buildTypes {

     release {
         productFlavors.flavorBlueTest.signingConfig signingConfigs.flavorBlueTest
         productFlavors.flavorBlueProd.signingConfig signingConfigs.flavorBlueProd

         productFlavors.flavorGreenTest.signingConfig signingConfigs.flavorGreenTest
         productFlavors.flavorGreenProd.signingConfig signingConfigs.flavorGreenProd
     }

     debug {
         testCoverageEnabled = true
     }
 }