Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 6

Sanskrit:

सोऽपतद्भ‍ुवि निर्भिन्नललाटोऽसृक् समुत्सृजन् ।मुञ्चन्नार्तस्वरं शैलो यथा वज्रहतोऽरुण: ॥ ६ ॥

ITRANS:

so ’patad bhuvi nirbhinna-lalāṭo ’sṛk samutsṛjanmuñcann ārta-svaraṁ śailoyathā vajra-hato ’ruṇaḥ

Translation:

Balvala cried out in agony and fell to the ground, his forehead cracked open and gushing blood. He resembled a red mountain struck by a lightning bolt.

Purport:

According to the ācāryas, the demon appeared reddish with blood, like a mountain red with oxide.