There is more to textures and materials than fits in a forum post, but here is a brief explanation related to your situation.
To illustrate, I have dressed my CC avatar with a black pullover:
The color of the clothing is determined by the black Base texture. Because the Base texture is so dark, the Diffuse color under Material Settings has little or no effect. If the Base color were white, changing the Diffuse color would have a visible effect.
You can adjust the Base color from within CC. Click the icon indicated in the screen capture to open the Adjust Color window:
This allows for only basic adjustments, but it is sufficient to give the black pullover some color, as shown below:
Another option is to open the texture in a graphics editor, by clicking the Launch button (marked in the first screen capture).
The graphics editor is set in the Preference settings by the user. If nothing has been specified yet, CC will ask for the location of the graphics editor executable: