Converts Hex to RGB

This is mainly curiosity, but I'm finding that when I hard-code the styles, it's converting the color HEX values to RGB.

For example,

<p style="FONT-FAMILY: Verdana, Geneva, sans-serif; COLOR: #cccccc; FONT-SIZE: 9px">Click here if you have trouble reading this newsletter.</p>

Converts to:

<p style="FONT-FAMILY: Verdana, Geneva, sans-serif; color: rgb(204, 204, 204); FONT-SIZE: 9px">Click here if you have trouble reading this newsletter.</p>

I hard-code all of my styles for HTML email newsletters so I'm wondering if this is going to cause a problem. What would be the advantage of converting the Hex value to RGB and could I disable it if I wanted to?

Thanks in advance,
Catherine