Cold water animals have a reputation for not being colorful, which is mostly true, but there are enough exceptions to the rule to fill almost any aquarium with color if you can find the right animals.
This was my tank back in 2009. I had kids, bought a house, got a long commute, and when my last octopus died in 2012 I decided I didn't have time for the hobby anymore. It's not just reef keeping, because I need to collect all of my own animals, so it also involves scuba diving, boating, yada, yada.... I just didn't have time.
But now my kids are old enough to want to go diving with me, and to want to learn how to design and build things, and learn about biology, so I'm thinking about designing a building a larger cold water reef tank, with all the same animals shown above, but more space, more gorgonians, more anemones, an automatic feeding system, and a gyre system (like Steve Weast's 400 gallon system) for massive flow.