CC Madhya 20.187

vraje gopa-bhāva rāmera, pure kṣatriya-bhāvana
varṇa-veśa-bheda, tāte ‘vilāsa’ tāṅra nāma
Word for word: 
vraje — in Vṛndāvana; gopa-bhāva — emotion of a cowherd boy; rāmera — of Balarāma; pure — in Dvārakā; kṣatriya-bhāvana — the emotion of a kṣatriya; varṇa-veśa-bheda — by differences of dress and color; tāte — therefore; vilāsa — pastime expansion; tāṅra nāma — His name.
Translation: 
“Balarāma, who has the same original form as Kṛṣṇa, is Himself a cowherd boy in Vṛndāvana, and He also considers Himself a member of the kṣatriya race in Dvārakā. Thus His color and dress are different, and He is called a pastime form of Kṛṣṇa.