अथ यदेतदक्षणः शुक्ल भा० सैवर्गथ यन्नील परः कृष्णं तत्साम तदेतदेतस्यामृच्यध्यूढ५ साम तस्मादृच्यध्यूढ५ साम गीयते ।अथ यदेवैतदक्षण' शुक्ल भाः सैव साथ यन्नील पर कृष्णं तदमस्तत्साम ॥ ४ ॥
In plain words
Now, the white brightness of this eye is indeed the ṛk, and what is dark and deep black is the sāman. Because this sāman rests upon that ṛk, it is sung as resting upon the ṛk. The white brightness of the eye is the ṛk, and the dark, supreme black is the ama and the sāman.
Close to the Sanskrit
Now, whatever is the white lustre of this eye, that indeed is ṛk. And whatever is the dark, the supreme black, that is sāman. That this sāman is mounted upon this ṛk, therefore the sāman is sung mounted upon the ṛk. Now, whatever is the white lustre of this eye, that indeed is ṛk. And whatever is the dark, the supreme black, that is ama, that is sāman.