[porphyra]

Blending the colors in Photoshop manually seems very tedious.

The open source Enblend/Enfuse, which ships as part of the open source panorama stitching software Hugin, does it automatically and seamlessly.

http://enblend.sourceforge.net/

[madaxe_again]

To be honest, PS’s inbuilt merge and stitch is pretty damn good - I use it on astrophotography outputs where I need to match subtly different processes between subframes of a mosaic. If there are flaws, they’re not ones my eyes can see.