There is a slight difference. This is from the Motorola website:
Dimensions
Black Ballistic Nylon
Height: 143.5 mm (5.65 inches)
Width: 73.3 mm (2.89 inches)
Curve: 8.3-11.2 mm (0.33-0.44 inches)
Metallic Red, Metallic Black
Height: 143.5 mm (5.65 inches)
Width: 73.3 mm (2.89 inches)
Curve: 7.8-10.6 mm (0.31-0.42 inches)
Weight
Black Ballistic Nylon
176 grams (6.2 ounces)
Metallic Red, Metallic Black
169 grams (6.0 ounces)