Whit in images becomes yellow with canvas functio

I use te canvas functions from quickpdf in my vb6 application.
This works fine except for one strange thing.
When I send an image (bmp) to the DC on some computers te white becomes a sort of yellow in the pdf. When i use the same DC routines to print to the screen and to the printer the white stays white.
This does hapen on my computer, but when I run the program on an other computer with the same operating system and the same windows theme everything seems ok.