I had cataracts surgery about 4 weeks ago with no problems, but for the past couple of days I have developed red eye and also a very itchy eye?

See your surgeon. Although the medicated eye drops used in cataract surgery can cause red, irritated eyes, there can be other causes for your symptoms. Allergies are the main cause, as well as conjunctivitis. Even if the vision is good and there is no eye pain, you should see your surgeon to be sure. You are far enough out from surgery for this not to be related, but it is a good idea to have it checked out.
Iritis. It is a good idea to go back and see your surgeon. Sometimes after catarct surgery patients develop this rebound inflammation, called iritis, and it can be resolved with anti-inflammatory eye drops. Usuallly this condition is also associated with pain, photophobia, and blurred vision. On the other hand, it can be just a simple condition such as allergies.
Allergies likely. Usually if there is inflammation from surgery, there is pain and light sensitivity. Go see your surgeon.
See eyeMD. Conjunctivitis (redness/inflammation of conjunctiva) after cataract surgery is not uncommon & can be due to: blepharitis, allergic (most common from drops), return of inflammation, viral or bacterial infection. See eyeMD to determine underlying cause & to rule out a dangerous, though unlikely, bacterial infection. More info: eyedoc2020@blogspot.com.