using cmyk textures doesn't mean that the final rendering also uses cmyk color space. final rendering is - and always will be - in rgb. if you are making it for print, it's better to convert it with photoshop or something similar (though psp has one of the best converting algorhythms for cmyk around), and tune it up here and there. also, you can add color profile of your target printing device. too much for ol' poser!