If a text LAYER is selected and you enter the color picker, you are able to select a text color from the Swatches panel. But if some text is HIGHLIGHTED and you enter the color picker, you are unable to select a text color from the Swatches panel; the computer just beeps at you. There's no reason this shouldn't work. It used to work in previous versions of Photoshop.
I am aware that, if you have some text highlighted, you can change the color of the text by clicking on a color swatch without entering the color picker. This is nice, but it should not be the only way to change the color of selected text.