The most common drug for colon cancer is called FolFox, with any drug there are side effects but they are tolerable, just remember that everyone is different even with the side effects. You can almost figure that what ever side effects you have after round 1 will carry through the treatment, but with each treatment some side effects will be more intense others will not. FolFox is a combination of drugs the one that seems to give the worst side effects is call Oxaliplatin. Here's a break down of what you can expect.
1st Day folinic acid and oxaliplatin are injected into the body by way of drips, this whole process of injecting these two drugs take about 2 or 3 hours. Yo will then be hooked up to a pump and receive 5FU. You will have the pump for about 46 hours. Most of us wear a belly bag that has the pump and the 5FU in it. Then you go back in and disconnect you. You don't have another treatment for 2 weeks.
The Oxaliplatin causes cold sensitivity, you can't drink or eat or touch anything cold during treatment and a few days afterwards. I recommend having gloves near by, getting something out of the freezer can actually burn you...it feels like needles sticking in your hands. You normally don't lose all of your hair it thins. With other chemo drugs your father may experience neuropathy, since he's a diabetic I'm not sure how advanced his diabetes is, but that too can cause neuropathy, numbness/tingling in hands and feet. I think walking and using your hands helps. I will do round 8 next week and I only have a little numbness in my right hand..more of a tingling. I recommend writing things down, any side effects your father experiences so that when you go to the Oncologist you will remember, he can adjust the dosage based on the side effects and how you are doing. (I'm almost 57 and also a diabetic)
The doctor will also probably write a prescription for a drug called Emend, it's an anti nausea medicine..it's just 3 pills. You take 1 right before you start your treatment and then in the morning for the next 2 days. My doctor also gave me 2 other anti nausea pills if I need them. I've never gotten sick, just feel nauseated. There's a lot of good information on the web and sites....Let me know if I can answer any other questions....Good luck