California Gnatcatcher coloration

From the Sibley and Petersen guides, the body coloration of the California Gnatcatcher is described and shown as gray. Same as photos found on Google. I have id'ed a male California Gnatcatcher at the Sorrento Valley Ponds by its dark tail and full dark cap. However, its body is visibly (and beautifully) blue gray. Is the blue gray coloration expected or have I mis-identified it?

Thank you,
-Kang
Source: SanDiegoRegionBirding Latest Reports