I believe what you're referring to, Lalita, is called "derivative work". Whether you paint over it, trace it, color it in, make a few or a lot of changes to it, or even make your own version of it, unless the specific terms of use of that image allow for derivative work to be displayed to the public (including on the internet), you're violating copyright. The copyright holder of the original image can give certain rights to others to make derivative works according to Section 106 of US Copyright Law.