You can manually set the values of CMYK to white by right-clicking on the layer in the Table of Contents and selecting Properties and browsing to the Labels tab. In the Text Symbol area, select the arrow next to the color patch and select More Colors. In the Color Selector dialog box, in the upper right drop-down menu, select CMYK and change all of the values to 0 and the labels will display in white. You can also use the RGB color model in the label expression: FindLabel = "<CLR red='255' green ='255' blue='255' >" & [NAME] & "</CLR>"