Combination Chemotherapy in Treating Patients With Colon Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. It is not yet known which schedule of chemotherapy is most effective in treating colon cancer. PURPOSE: Randomized phase III trial to compare different schedules of chemotherapy using carboplatin with fluorouracil and leucovorin in treating patients who have stage IIB or stage III colon cancer.