improving color stack in xdvipdfmx

[Ulrike Fischer]

xdvipdfmx has a color stack but it is missing some features compared
to the color stack(s) in pdf/luatex  

At first there is only one color stack, that makes it difficult to
add support e.g. for transparency.

But more importantly one can only put rgb, cmyk and gray values on
the stack. There seem to be no way to store also a color model. That
means that while one can define and use tints from a separation
color space ("spot colors") as shown in the dvipdfmx manual, it is
not possible to use them for running text going over a page break. 

Would it be possible to improve xdvipdfmx here?

-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/