OPI GelColor is gel nail polish with a thin, brush-on formula designed for high performance and a glossier finish compared to a regualr nail polish. Design house: OPI. Gender: Ladies. Category: Nails. Collection: Gel Nail Polish. SubType: Polish. Beauty group: Nails. Size: 0.5 oz. Color: Black Onyx. Barcode: 619828090409. OPI Ladies Gel Nail Polish 0.5 oz Black Onyx Nails 619828090409.