Many buff-striped keelbacks are less colorful than these.
It was back in the 1980s that I made the acquaintance of the natricid (garter, water, and related snakes) species.

Chris had received a shipment from Bangkok, and along with the cobras, kraits, and pipe snakes, was a bag identified only as “keelbacks.” Upon seeing the designation I immediately thought Rhabdophis, a keelback with a virulent toxin. But when Chris opened the bag it contained something very different—a keelback species that I didn’t recognize.

Several of the snakes were similar to each other in body color, being an olive tan (with vaguely bluish interstitial skin) and having a buff colored dorsolateral stripe along each side. The light stripe was indistinguishable on the neck but very apparent on the posterior three quarters of the snake. The heads of these were also olive-tan with black vertical interstitial markings on the upper labials. Most bore broad black bars from lower side to lower side but where the dark bars crossed the light dorsolateral stripes, the latter were markedly lighter. The black barring was most prominent anteriorly, faded posteriorly and was absent from the rear of the body and the tail.

But then there were the odd 3. On these the patterns were the same but the colors differed greatly. On these the head and neck were a rich orange. The scale sutures of the yellow upper labials were black. The ground color was rich olive tan and the dark cross barring was hardly any darker.The light stripes were buff anteriorly but shaded to a rather bright yelliow posteriorly. And trhe interstitial skin of the body was pale but definite blue.

Can you say “pretty?” I sure did, and these 3 snakes were with me for many years, thriving on a diet of ranid frogs.
Strangely, although I have since seen several shipments containing this species, I have never again seen the orange headed form. Beginner’s luck I guess.