Ramayana
हंसानां हि पुरा राम नीलवर्णः सपाण्डुरः । पक्षा नीलाग्रसंवीताः क्रोडाः शष्पाग्रनिर्मलाः ॥ 7-18-33 ॥
For formerly, O Rama, the color of swans was dark mixed with pale white; their wings were edged with dark, and their breasts were spotless like the tips of young grass.
english translation