Photoshop :: Change Color Of Globe

I'm writing a coursework about banks and need to insert a picture, which shows the globe in unrealistic greenish color. Someone told me about Photoshop, that it has eyedropper and fill tools. But I really feel missing with all those complicated tools and get tired of trying to understand what is what. replace the greenish color of the globe with blue one, so it looks more like of the same color as the bottom book from the stack. The rest of the things on the pic should remain the same with their colors. URL....