White is the absence of color and therefore ink. Make sure the background is perfectly white and you shouldn't have any problem since nothing will print.
Thank you BobLevine. OK, I understand. I do not have to worry then because white in CMYK is no color.
However, that's make me wondering of another scenario:
Let's say that I am going to print on a coloured paper like light green, or light grey or something like this. I have an image that has some white in it and I want to make sure that the white in the image stays exactly white on the coloured paper. I don't want the white in an image to default to the paper colour. I want it to stay very white like #FFFFFF on screen.
How do I achieve this?
The only way to print white onto a colored stock is use white ink, which is going to add a lot of expense (if it can be done at all in the workflow at the printer). But in full-color work the process is typically to print the background color onto a white sheet rather than using pre-colored stock.
OK thank you Peter.