the reason it looks brighter is because you are both using far fewer colors to shade Inu, and because the base skin color you use is brighter.
Also, if you're doing ALL of your sprites yourself in this style, these wouldn't be issues. However, since you probably aren't, you should consider the fact that your outlines are black, while the ones of the RTP sprites are dark shades of the base colors of the area said colors are outlining.