In terms of visibility, the Nanometre values that are nearer to 550nm are better than values farer away.
Please see the visibility curve below:
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Due to this chart, the 473nm is best visible. However, this color is more cyan than blue, and thus cannot create a good royal blue. In terms of color spectrum the 473nm is much worse than the 445nm.
The 405nm blue in contrast is nearly not visible and thereore needs a lot of power to become visible. As there is not much advantage (and even some disadvantages) compared with the color spectrum of the 445nm, Laserworld decided to mainly feature the, as we think, optimum visibility - color-range combination.
For OPSL systems we often use a combination of several blue color ranges to get a better colro spectrum. Please ask us if you need further details about that.