CSS for SAPUI5 controls

Hi Experts,

I tried to apply CSS to the SAP UI5  button control as below.

In the CSS file:

.myButton

{

              color: red !important;

  font-size: 14px;

              background-color: Grey;

}

in the Java script:

Button4_c2c5.addStyleClass("myButton");

But the CSS didn't applied.

Can any one tell how to apply CSS to SAPUI5 controls?

Regards,

Naga.