There are different methods of changing colors of layers, depending on what file-type and software you open the graphic file with.
For example, if the file-type of the graphic is Adobe In-Design, the steps to changing the color will be slightly different from changing the color of a Photoshop graphic (although very similar).
You can easily change colors of a graphic file in Adobe In-Design by doing the following (also shown in the screenshots below):
Select the layer that you'd like to change the color of
Select the Color Picker from the tools pane
From the Color Picker popup, select the desired color from the color square and hue adjuster
Select OK after picking a color