A spinnable rotor for a high speed centrifuge includes a housing which defines a chamber interiorly thereof for receiving a whole blood sample and for containing a predetermined amount of red blood cell absorbent gel. The housing includes an upper portion and a bottom portion, the upper portion having a port formed through the thickness thereof. The upper portion has at least a portion thereof formed from a light transmissible material. A light pipe is joined to the upper portion and light transmissively communicates with the light transmissive portion of the upper portion. The light pipe extends at least partially into the chamber and has an open, lower free end. When whole blood filling the rotor chamber contacts the lower free end of the light pipe, the red color of the blood is transmissively communicated to the upper portion of the rotor housing where it is viewable by the user of the centrifuge.