If you write
Color.Lerp(Color.white, Color.red, 1.0f);
that’s the same as simply writing
Color.red;
The final parameter (1.0f) denotes the progress/position of the LERP, not the time or speed. So
Color.Lerp(Color.white, Color.red, 0.5f);
would return a color midway between white a red.
If you you intended to made the color fade in that script, here is how it would work:
http://pastebin.com/xQAfEwAR