One would have to compare them to known genuine PB chips. Having said that, not all PB chips were UV tagged. Some of the color variations (such as the different blue shades on the $1 PB) will glow, while others will not. This is what created the color variation. Because a PB chip does not glow when subjected to black light UV tube, does not necessarily mean it is not genuine.

UV tagging is a specialized field in chip collecting that I have not really delved into, but I know that some collectors actively make such comparisons and have recorded them.