metastatic colon cancer
has got bad prognosis. It is stage 4 disease, liver metastasis explains his yellowish discoloration of eye, but extreme weakness and drowsiness
may be due to brain metastasis
, so brain CT scat can be done. If brain mets found there is a scope of palliative radiotherapy to brain which may at least increase his quality of life. Or due to liver mets hepatic encephalopathy
may also be precipitated . Consult your doctor. without knowing the exact cause life expectancy can not be predicted.