Future Value

As I was doing calculation for future value; all the numbers turned red. I right clicked the number to format cells; after I clicked numbers tab. The only other options were in parenthesis or negative sign. I also went on to text color and tried changing it to black and it still wouldn't. I got the calculations right, it is just that the color turned a different color. Is there a reason to why this happened? What can I do to fix it?