"Do you have a suggestion on how I can get the white areas on my renderings to appear more white than gray?"
One trick is to use the brightness tab to make the whole rendering brighter.
Here I increased the brightness from 50 to 60 to make things brighter.
Another trick is to apply "self glow" to some materials to make just that material brighter.
See this article:
I've added a 20% glow to a color and painted some elements with that color. I see no difference however when I render. Is there a setting in the render dialogue that needs to be looked at?
When you adjust brightness, experiment as well with lowering the brightness a little, and then increase the image contrast. Also - you can use "burn" - but this one in particular will require very small adjustments.
When your rendering environment is a blue sky, white surfaces are going to be cooler - so not pure white but with some amount of blue.
So don't ignore adusting color saturation as well - lowering saturation can be very helpful when you're trying to improve on white.
One of the nicest thing about these features is that you can make these adjustments while your rendering is processing, which I think is a real advantage.
"I've added a 20% glow to a color and painted some elements with that color."
I just tried this, and something about self glow seems to be broken.
We'll look at it next week and put out a new version with a fix Tuesday or Wednesday