Red-sided / Valley
A variant of Common Garter Snake (Thamnophis sirtalis)

Representative Common Garter Snakephoto — a dedicated image of this exact morph isn't available yet.
A natural regional form (T. s. parietalis / infernalis) showing vivid red or orange bars and flecks along the flanks between the stripes. Strikingly colorful wild type.
Keeper tips for this variant
Red-sided stock often comes from cool northern climates and benefits from a genuine cooler brumation period in winter to stay healthy and breed well.