Illustrator CC: how do I change the artboard colour?

This really should be in the artboard options rather than hidden away in preferences. Maybe user would double-click artboard with artboard tool to access options then set a simulated background color. Or maybe some floating popup when selecting an artboard that allows you to quickly select a color from library as the simulated background. That way you can have a mix of different artboard colors and not have to worry about drawing rectangles, sizing and aligning them, sending them to back and locking. And it wouldn't affect the default setup of blank artboards as the user would have to deliberately change it via artboard tool. The only issue might be that on export, you could forget which artboard colors are simulated and end up with a transparent graphic. But you could potentially also have some quick option like "fill colors to all selected artboards" that would generate artboard-sized rectangles based on the selected simulated artboard colors (or a newly selected color) on each artboard, then auto-send the layers to back and lock. Or maybe some option to toggle all simulated backgrounds on or off so you can quickly see which artboards are which. But I don't know the exact mechanics of Illustrator, or how other users might use it, so perhaps there is a reason it has been setup in this way.

I know it's not a long process to draw rectangle, size to artboard, send to back and lock, but I usually end up doing this so often that it really should be just a quick artboard option by now. My workflow is organised such that I usually keep each color variation of a design on a separate artboard anyway, hence why a quicker way of generating artboard colors would be handy. And most of the time, I need what I'm designing to work on a variety of background colors, so I will usually always have several variations on separate artboards. Usually black, white, and two color options.

Honestly, I never thought I would say this, but I feel like inscape is more capable than illustrator for certain tasks. Right now I am trying to design a set of Icons for an application that has a dark theme by default. I paid to upgrade to illustrator because I found inkscape sorely lacking in the past. However, inscape isn't lacking as much as I thought. It has had a couple of major version releases that included more tools, and a robust feel. The best thing about inkscape though is how customizable the environment is. If you want to develop a logo that will be placed in a black envfironment, you simply create a dark logo (or dark icon) profile, choose a dark color of your choice for the artboard, then save. You will forever hav a preset environment. These may seem like small little things, but when it comes to having a smooth work flow, these little things are what makes and brakes the quality and speed of a work-flow that a piece of software provides. Its honestly down right luaghable that you cannot choose a preset in illustrator for dark themes &/or environments during a time when dark is very popular. Get it together Adobe.

I have made the most simple way.  I have created a black shape with my artboard size and sent it back

Go to FILE>DOCUMENT SETUP>click on SIMULATE COLORED PAPER
Change color of upper color box to the desired color.
Click OK

If it does not change the background color press CMD + SHIFT + D twice. It should work.

It's just the way it is. If you want all your artboards to share the same color, create a giant rectangle that covers the entire work area, then all artboards will share the same base color. Change the color on all layers by changing the color of the single rectangle. Or you could use a global color and change the global color build in the swatch panel.