Canto 3 -
Araṇya-kāṇḍa
Chapter 52: Rāvaṇa Again Abducts Sītā
Text 3.52.31

तरुप्रवालरक्ता सा नीलाङ्गं राक्षसेश्वरम्।
प्राशोभयत वैदेही गजं कक्ष्येव काञ्चनी॥

taru-pravāla-raktā sā nīlāṅgaṁ rākṣaseśvaram
prāśobhayata vaidehī gajaṁ kakṣyeva kāñcanī

taru-pravāla-raktā = colorful like the newly grown sprouts of certain trees; nīla-aṅgam = the dark-limbed; rākṣasa-īśvaram = lord of the rākṣasas; prāśobhayata = sparkled against; vaidehī = Vaidehī; gajam = on an elephant; kakṣyā = belt; iva = like; kāñcanī = a golden.

Colorful like the newly grown sprouts of certain trees, Vaidehī sparkled against the dark-limbed lord of the rākṣasas, like a golden belt on an elephant.1

Just as the belt on an elephant subjects the elephant to the control of its rider, it is implied here that having come to Rāvaṇa, Sītā-devī subjected him to the control of Lord Rāma.

1 Rāmāyaṇa-bhūṣaṇa: taru-viśeṣa-pravālavat raktā pīta-varṇā. “tena raktaṁ rāgāt” ity atra rāga-śabdo hi varṇa-mātre prayuktaḥ. The quotation here is Aṣṭādhyāyī 4.2.1.