Double check your Character Settings: you may have something odd like Stroke Over Fill selected. And don't forget to highlight the text when you do this, or nothing will take effect.
If Dave's suggestions don't help, show us screenshots and give exact steps to tell us what you're trying. We need details in order to know how to help you.
The text layer must either have all text selected with the text tool or the layer must be selected in the timeline with the selection tool to change the font color in the Character Pannel.
If that doesn't work, select the text layer in your timeline, press the U key twice to reveal all changed properties. If you don't see fill color then drill down until you get it and change it there.
If that doesn't work we need a screen shot with all properties of your text layer revealed.