My current project is at:

You will see the following image in use as part of the background:


The problem is that this image was a different color at one time. I used the paint fill option in the Seashore paint program to change the color of this graphic to green. When I uploaded it to the website, I noticed that it had jagged edges from the previous color. So I started repairing the image using tiny gradients lines, which were each about 3 pixels wide, that went from green to a transparent color. It is indeed doing the job, but after two hours I realized there has to be a faster way. Can someone point me in the right direction? Or would it be easier to just have someone make a whole new image using this green color?

Thank you!