EVERYTHING is optional. -- NOTHING is forever.

Here's the background. RGBA was added for three purposes.

First, and primary, is that it gives an illusion of items floating over or under a menu, etc. That feature alone alerts the mobile user that information may be above or below what is currently on the screen.

Second, it removes some of the "harshness" that results from using web-safe colors (did you know there are only 216?!?). Anything other than a web-safe color is just throwing the dice and hoping the customer's browser will get close to the color you selected.

Third, it was not added in case the browser could not handle hex but, the hex was added for browsers that could not handle the rgba as rgba and css3 are the next steps in web design. In fact, the browser has to accept CSS3 in order for the rgba call to work. You can google "css3 compliant browsers" to get a gist of which ones work presently.

That said, I have to reemphasize the beauty of open source. DO WITH AS YOU PLEASE.

If you want strict colors, either remove the rgba calls or change the percentage to 1 from 0.whatever. Shouldn't be any problem unless you miss a 0 or . in your replace.
Some would say you might be "clinging tenaciously to the trailing edge of technology."