From:
Yes, to change its size, press Ctrl+T in Photoshop to transform it, and drag its corner out, while holding Shift (this prevents distortion). If you keep it on its own layer, you should be able to this at any time, not just after you've dragged it in. If you want to change the colour of the object you've dragged in, it would depend on what kind of object you've dragged in. If it's a photograph, that will be hard. If it's a diagram of some sort, you can always try using the Hue/Saturation sliders (by pressing Ctrl+U). You then select the colour you want to change, and move the sliders to change it. I hope this helps :)
