There are a few options when your colors are naturally dark on the model.
Turn on Display Component Colors. This puts temporary artificial coloring on the components for the reason you are asking.
- Shift + N (hotkey combo)
- Or go to the Inspect menu > Display Component Colors
Turn off the effects: Object Shadow and Ambient Occlusion.
- Go to the navigation bar (toolbar located in the center, at the bottom)
- Find these items on the Display Settings menu, under Effects.
Try the different environments, from the same navigation bar menu, Display Settings > Environment.
Or, temporarily apply a different material appearance. There is a trick to help you manage this.
- If you apply a lighter shaded color, say grey instead of black, there will be a grey and black swatch hosted in the "In this design" portion of Appearances.
- When you are done modeling, and need to do a rendering or see the design in the intended color scheme, drag the darker swatch onto the lighter swatch, in the dialog.
- This will replace all instances of the lighter shade with the darker shade.

Please let me know if this helps.
Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.