Is it Ukraine or Russia that the EU regarded as a resource colony?

Both countries fulfill the role of being large commodity exporters.

Also, with Nordstream was Russia desiring to partially fulfill that role while also trying to maintain/develop their own economic sovereignty?

Likely it was to get around piping gas through overland routes. You can see from this map that there were already pipelines into Germany, but as the attached paper describes, some of these lines have been shut off in the past due to political crises, which has fueled the creation of new overseas lines (such as the south stream)