Alright buddies, your can choose for photography editing. This kind of software are plentiful these days.

We have to choose between LIGHTROOM, GIMP or CS5. Just for this time, we use LIGHTROOM:
STEP 1: In LIGHTROOM, go for "Graduated Filter".
STEP 2: Then load your photographies into LIGHTROOM and load into "Development Module". Select the tool and adjust it right to your wanted direction.
STEP 3: Choose your ideal color.
STEP 4: Find the results.

LIGHTROOM is such a wonderful software that many pro photographers fall deep into it. It can change the photo effects to meet your creation if you use it properly. Keep learning more and create more! Besides, do not forget to watermark images after done.