Generally speaking, the closer you get to the UV wavelength range of 200-400nm, the worse exposure over time is for your eyes (and your DNA/skin). It's the same reason they put warnings on black lights about exposure because they can cause eye damage and/or DNA mutation/premature skin aging.
That said, in a pinball with spot usage that's not always on, it would be less cut and dry of a case than an always-on or mostly-always on situation. But more information about the specs of the light wavelength in given products with blue and purple lighting is always better so people can weigh the risks and make an informed choice.
Here's a wavelength chart I grabbed off the internet to help visualize the light wavelengths on the spectrum:light-wavelength-frequency (resized).png