I'm not sure what was happening with the colours (or even for certain where you might have been changing them), but to be considered "your" first skin, you'd need to make every part of it yourself.

If it's based on someone else's work and you've just tweaked the colours then it's not new work I'm afraid.

In Skin Studio, if you double click on an item it should open your default graphic editor. If you then design and make new graphics to replace those default graphics, then it would be your skin.

If you don't have a good graphics editing program, this process will be almost impossible, so you may need to start by getting something like PaintShop Pro and learning how to use it. It also might be a good idea to sketch out how you want the final skin to look before you start.

Have fun, and as you make progress you can show off your work by making a screen shot of it as your desktop image in your profile

Tools-preferences-editing-add whatever program you want to use.Move it to the top.