अथ यदेवैतदादित्यस्य शुक्लं भाः सैव साथ यन्नीलं परः कृष्णं तदमस्तत्सामाथ य एषोऽन्तरादित्ये हिरण्मयः पुरुषो दृश्यते हिरण्यश्मश्रुर्हिरण्यकेश आप्रणस्वात्सर्व एव सुवर्णः ॥ १.६.६ ॥
In plain words
Now the white light of the sun is sā, and the dark blue that is beyond black is ama, and that makes sāman. And the golden person who is seen within the sun, with a golden beard and golden hair, all of gold to the very tips of his nails —
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
रण्यकेश इति, ज्योतिर्मयान्येवास्य श्मश्रूणि केशाश्चेत्यर्थः । आप्रणखात् प्रणख नखाग्र नखाग्रेण सह सर्वं सुवर्ण इव भारूप इत्यर्थः ॥
In plain words
The expression 'Golden-haired' means that his hair and beard are made entirely of light. Right down to the tips of his nails, his entire form is radiant like gold, possessing the very nature of light.
Close to the Sanskrit
As 'Golden-haired', meaning his beard and hair are made of light indeed. Right up to the nail tips, along with the nail tips, the entire form is like gold, having the form of light, this is the meaning.