After generating PDF the text color is not displaing as it is

Hi,

I have 1 graph bar report, in that all bars color is red and the label which is presend in that red bar is white colored.

when i generate the PDF then that white label color is displaing little bit Gray. But i want to show that label color as white as it is. Don't know how that color is displaing like Gray.

please view the attached images.

Graph in Preview :  https://i.stack.imgur.com/N8Iwg.png
Graph in PDF :  https://i.stack.imgur.com/2WS8Z.png

Thanx