Probally and incredibly stupid question

So I just started using Photoshop to color my sketches but I've come across a problem. I select a color but when I try to paint, it comes out gray... I've tried a few things I've thought of but since I'm not familiar with the program yet, I'm not sure what to do.

When you open a new document make sure the colour mode is set to RBG and not Greyscale

Or if this is happening when you open up a picture then try this ....

Image>Mode>Make sure RGB Color is selected


hope i helped