When working in a visual medium, how do I avoid incorrect color?
As photographers know, the color of light is usually not white, and when working in your home, you're often working under tungsten bulbs (or similar) which have a warm tone to the light or with fluorescent which have a green cast. Because your brain is pretty good at making what you think should be white look like white, these lights can cause your eyes to see the colors differently and, as a result, change the way you mix or blend in your work.

As with photography, we can control the light we use and select for what our eyes naturally tend to, which is daylight. Where possible, you should light your work with dedicated lamps using daylight balanced light bulbs with a color temperature in and around 5500K. The packaging should specify the color temperature, which is more reliable than if it merely says daylight on the package, so avoid those that don't or that claim a temperature way off that number. 

I really recommend getting some decent swing-arm desk lamps and LED bulbs. Not only are these lamps cheaper, but they're usually a lot brighter and much easier to position, especially with easels. LEDs are really efficient and they don't heat you up when working in close quarters, making for a more comfortable experience.