contrary to popular belief, sea run cutthroat do not stay chrome while in the rivers, bluebacks as they may be, it does not remain that way for very long. The color of the fish does not determine whether it is anadromous or not especially when caught that far above any salt water.
they color up just like a salmon or steelhead after being upriver for an extended period of time. i have caught sea runs while fishing for salmon and steelhead that are very colorful. In the wilson,nestucca,trask,salmon,and siletz i have caught resident cutthroat up to 12 inches, but most anything larger than that is usually a sea run fish.It's also believed that sea runs will only enter the rivers in fall, and while it's true the largest push is in the fall, i have caught chrome bright sea runs and colored up sea runs 20 miles upriver in the middle of july and august.
that is most definitely a sea run cutthroat.
i attached a pic of the face of a 16 inch sea run i caught while steelhead fishing a few years ago. notice how colorful the fish is.