src/java.desktop/share/classes/com/sun/imageio/plugins/png/PNGMetadata.java

@@ -1880,10 +1880,11 @@
                         int blue = getIntAttribute(child, "blue");
                         if (red == green && red == blue) {
                             bKGD_colorType = PNGImageReader.PNG_COLOR_GRAY;
                             bKGD_gray = red;
                         } else {
+                            bKGD_colorType = PNGImageReader.PNG_COLOR_RGB;
                             bKGD_red = red;
                             bKGD_green = green;
                             bKGD_blue = blue;
                         }
                         bKGD_present = true;