How to change the text color of a label by using RGB values without changing the background colour?

xCode interface builder:

When I try to change the color property of a label's text by using the RGB values, the background color also changes to the same value automatically.

in other words:

While setting the RGB values for text colour of labels, the background colour also changes unless we use the sliders.

How to make sure that only the color of text changes and not the background?