I can see that affecting color, but making the work appear too dark (or light)?
Yeah, I should've been more clear on that.
Note the contrast relationship between the two calendar photos I posted. There's a big difference in character of light has on contrast relationships between diffused window light and direct somewhat diffused artificial light in the CFL.
Somewhat low and diffused light tends to dim the surface and change the contrast relationship that compounds the appearance that the image looks dark when it really primarily has lost contrast. It's the same effect viewing matte paper vs glossy prints. Blacks fog up and whites go flat but you can still distinguish between the elements in the image. It just has lost "Pop" or clarity and definition.
Painting with the sun coming through diffused white curtains gave plenty of adequate light that didn't change contrast but throughout the day as the sun moved over the house there was less light but the character of light had diffused even more causing me to rework paintings into making blacks next to shadow detail even more dense and highlights even more brighter with a boost in saturation throughout the image.
When I finished and looked at the canvas under a spot/flood tungsten lamp or in direct sunlight the painting looked gaudy and cartoonish primarily from contrast ratio changes.
That's why I go by a grayramp to examine the gradualness of the increase in tone from black to white just for a reality check.