We sent out a rendering tip today about White Walls.
Boothy pointed out that you can also make quick adjustments to walls using the Material/Color channels feature.
Here is a rendering of a house which we used for our first Webinar:

By clicking on the material in the back wall, you can select Change Color

This brings up a Wizard which lets you make changes to the color of a material after rendering.
Here I changed it to HSL (rather than RGB) mode, which lets you set the luminance of the color directly. And used the slider bar to move it more towards white.

I was able to adjust the wall with the slider until I got a lighter effect.
Note Material Channels does not re-render the model, so if you change the color too much, any anti-aliasing at the edge of the color will not be changed properly, and also any reflections of a color will not be changed. But it can be a good idea for Walls.
See: Material Channels
Boothy pointed out that you can also make quick adjustments to walls using the Material/Color channels feature.
Here is a rendering of a house which we used for our first Webinar:

By clicking on the material in the back wall, you can select Change Color

This brings up a Wizard which lets you make changes to the color of a material after rendering.
Here I changed it to HSL (rather than RGB) mode, which lets you set the luminance of the color directly. And used the slider bar to move it more towards white.

I was able to adjust the wall with the slider until I got a lighter effect.
Note Material Channels does not re-render the model, so if you change the color too much, any anti-aliasing at the edge of the color will not be changed properly, and also any reflections of a color will not be changed. But it can be a good idea for Walls.
See: Material Channels