Human standard white light is by definition a combination of colors and cannot be replicated using a single wavelength (monochrome). There are two ways to do something similar to do this.
In the First method, everything will look one color (make it green to ensure it being human friendly) and its shades. This can be accomplished by a filter in the atmosphere, reflecting all other wavelengths. As a bonus, this could be a terraforming mechanism to reduce incoming light, thus cooling the planet. Obviously, for locals, who are adapted to monochrome light, thus will have only single color cones, seeing everything in gray. But for humans, the planet will look colored.
The second way of doing this will make everything look grayish, even for humans, but will not be very hospitable. Humans see monochrome in low light situations using rod cells. But in order to do this, your planet should be very dark. In time humans will adapt. I read somewhere it would take more than a day in the dark for human eyes to reach its limit on low light vision. Thus local human populace would be adapted for this planet.