Hi there,

Lowry protein assay gives a stable coloration between 650 and 750 nm. As long as you measure all samples at the same wavelength, it will be OK.

I agree. As long as the wavelength in that range it should be O.K. except the wavelength with the highest absorbance will give you the best reading if you expect to see the difference.

I too agree.  We have to use same nm to standard and sample to get more accuracy.

It will make a difference, since the more accurate result is at 750nm.