Colour-polarizing filters?

[athbr]

Was browsing through Horenstein's Colour Photography book and found this interesting passage about color-polarizing filters that produce varying intensities of a colour (or sometimes multiple colours) as you turn the filter.

Yet I haven't been able to find any information about these online much less any available to buy.

Anyone know about this?

The passage in question is attached.

 

[rbrigham]

Cokin made these and they show up on ebay from time to time
there are red and blue ones on at the moment

stay safe

robin