pneumonia pathological phases of

Shortly after this congestion occurs the phase of red hepatisation in which there is a massive outpouring of polymorphonuclear leukocytes accompanied by intra-alveolar hemorrhage.            

Many of the red blood cells undergo lysis.

These cells, together with polymprphonuclear leukocytes, produce the rusty sputum.       

Because the firm consistency of the affected lung is reminiscent of the liver, this stage has been  named "red hepatization".  

Source:  HARSH MOHAN PATHOLOGICAL BASIS OF DISEASE