Properly initialize color hinted vec4 uniforms to 0,0,0,1 fixes #9354

drivers/gles3/rasterizer_storage_gles3.cpp

@@ -2497,7 +2497,13 @@ void RasterizerStorageGLES3::_update_material(Material *material) {
 				//value=E->get().default_value;
 			} else {
 				//zero because it was not provided
-				_fill_std140_ubo_empty(E->get().type, data);
+				if (E->get().type == ShaderLanguage::TYPE_VEC4 && E->get().hint == ShaderLanguage::ShaderNode::Uniform::HINT_COLOR) {
+					//colors must be set as black, with alpha as 1.0
+					_fill_std140_variant_ubo_value(E->get().type, Color(0, 0, 0, 1), data, material->shader->mode == VS::SHADER_SPATIAL);
+				} else {
+					//else just zero it out
+					_fill_std140_ubo_empty(E->get().type, data);
+				}
 			}
 		}