Hi Mellissa, I'm relatively new to Colchester myself but grew up nearby, and can say that it's generally pretty diverse culture wise. I personally think it helps that Colchester is predominantly an army town, and the recruits can come from all over on assignment. Some people are put off by this, but personally it doesn't bother me. We just bought a house on ex army land, which is surrounded by active barracks, I can literally see one about 100ft from my house, but they never bother us in anyway. On my development there are two black African families about 10doors down from me, both with young children, and further down there are a Spanish family of 5 and French couple. I am half-iranian myself, so I'd say it's pretty diverse.
The only areas I was told to avoid when moving here was Monkwick and some parts of Stanway. But then I know a few people who live there and say its fine! Nice areas I was told Prettygate and Abbey Fields. Highwoods is right next to main roads and hospital, so quite busy. We're in between Monkwick and Abbey Fields and it's a really nice quiet area. About 15mins from town which I prefer. Also you have Castle Park in the town centre which the park is free to enter, and great for families, especially in the summer.
My sister used to live in a small village right outside Bristol and worked as a nanny there, and although she loved living there, she didn't have a very high opinion of the equality and diversity in the area. But thats just one person's opinion.
Hope you find somewhere, and sorry for long post and hijack!