The dorsal fur of Oligoryzomys flavescens consists of bright orangish-brown hairs mixed with blackish hairs, the hairs on the flanks are all orange and the underparts are yellowish-grey. The boundary between the upper parts and the underparts is indistinct, grading from one colour to the other.
The dorsal fur of Oligoryzomys flavescens is composed of orange-brown hairs intermixed with black hairs, the flanks have all orange hairs, and the underparts are yellowish-grey. The boundary between the upper parts and underparts is indistinct, transitioning gradually from one color to another.