What would I need to look into for effects I can apply to images in XNA 4.0?

What I want to do is smooth the edges of the places where the color comes in contact with the (blank) back ground, then I guess you could say 'Chroma Key' out a few colors, then change the way a few colors look. (Like change dark blue to light green, etc). Is this possible? If so what Do i need to look into in XNA?

Below is the image (which will be downloaded anew every time the program is run) that I want to apply the said effects too.

[attachment=7428:CLE_N0R_01.gif]