diff --git a/skimage/color/colorconv.py b/skimage/color/colorconv.py
index ba670ddb..fc9ab342 100644
--- a/skimage/color/colorconv.py
+++ b/skimage/color/colorconv.py
@@ -52,7 +52,7 @@ __all__ = ['convert_colorspace', 'rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb',
            'rgb_from_gdx', 'gdx_from_rgb', 'rgb_from_hax', 'hax_from_rgb',
            'rgb_from_bro', 'bro_from_rgb', 'rgb_from_bpx', 'bpx_from_rgb',
            'rgb_from_ahx', 'ahx_from_rgb', 'rgb_from_hpx', 'hpx_from_rgb',
-           'is_gray'
+           'is_rgb', 'is_gray'
            ]
 
 __docformat__ = "restructuredtext en"
@@ -62,6 +62,17 @@ from scipy import linalg
 from ..util import dtype
 
 
+def is_rgb(image):
+    """Test whether the image is RGB or RGBA.
+
+    Parameters
+    ----------
+    image : ndarray
+        Input image.
+
+    """
+    return (image.ndim == 3 and image.shape[2] in (3, 4))
+
 
 def is_gray(image):
     """Test whether the image is gray (i.e. has only one color band).
@@ -641,7 +652,7 @@ def gray2rgb(image):
         If the input is not 2-dimensional.
 
     """
-    if (image.ndim == 3 and image.shape[2] in (3, 4)):
+    if is_rgb(image):
         return image
     elif is_gray(image):
         return np.dstack((image, image, image))
diff --git a/skimage/color/tests/test_colorconv.py b/skimage/color/tests/test_colorconv.py
index 470fd168..3365bb1c 100644
--- a/skimage/color/tests/test_colorconv.py
+++ b/skimage/color/tests/test_colorconv.py
@@ -29,7 +29,7 @@ from skimage.color import (
     rgb2grey, gray2rgb,
     xyz2lab, lab2xyz,
     lab2rgb, rgb2lab,
-    is_gray
+    is_rgb, is_gray
     )
 
 from skimage import data_dir, data
@@ -255,14 +255,16 @@ def test_gray2rgb_rgb():
     assert_equal(x, y)
 
 
-def test_is_gray():
+def test_is_rgb():
     color = data.lena()
     gray = data.camera()
 
+    assert is_rgb(color)
+    assert not is_gray(color)
+
     assert is_gray(gray)
     assert not is_gray(color)
 
 
-
 if __name__ == "__main__":
     run_module_suite()