Kevin,
The interior of the mouth of a healthy green anaconda is usually a combination of different shades of gray color. You shouldn't see much in the way of pinks or reds that you would typically see with most other boas or pythons. The Latin species name for the green anaconda, murinus, refers to the gray color of a mouse. There is some debate over whether this is in reference to this gray color of the interior of the mouth, or the very gray coloration most greens exhibit when they become opaque just before a shed. Attached is a photo of one of my females displaying the possible reason for the name murinus.

Kelly