Just to make sure this isn't a brightness vs. expectations issue:
Yeah, in person the lightsabers will not have that solid white core you see in the movies. A lot of people, I think, go in expecting that. That appearance shows up on camera, but you won't actually see that in real life. What'll happen as the light gets brighter is the intended color, the blue, will become more bold and uniform and the glow will be a bit larger. So ideally the lightsaber will wind up looking just a uniform color in this scenario.
As an example, while my deep red blade may look like this in a photo:
what it actually looks like is this:
but with a much larger glow.
However, if the blade is so dark that you can still see the whitish color of the blade stock through the light that may be an issue. For me that has typically stood out in amber blades.