Yes; I don't have imgflip pro. Next to the place where you enter the desired caption, there will be two boxes colored white and black. Those are the text color and text shadow color, respectively; selecting either of them will allow you to change them. I would recommend using complementary colors and colors that stand out from the background image, as it will make your caption more legible and noticeable. Next to those boxes will be a box with the number "5" marked in it. This is the font shadow size, which you can also change. There are also more options available such as changing font size, moving text boxes, adding text boxes, et al.