You can also click on the "dropper" tool and access a color or shade already in the image. That will give you a palette within the image (or to create a new pallete, as Radjehuty suggests, within the program), and then go to the "T' tool within which to choose font style and size. Note that you can change the font, size and color as well as the text itself and even move if you left-click the mouse and create a 'box" within which to work the text. This will make the font color compatible with the image.
Click on the text layer under layers, then click on the text icon on the left, then look at the top of your screen and click on the little box with color in it. Then pick the new color you want.