ROM Hack need help pls!

[raiza light]

so im trying to make my own soul silver hack using storm silver as base rom, and my aim is:

• to replace all the back sprite with the ones from white and black so tht all the pokemon can appear and not just the head
• to replace male form with mega evolution form ex: (male charizard with charizard X)
• to add some unova and kalos pokemon with their overworld sprites by discarding some old unloved ones xp

so far i have replaced all kanto's pokemon back sprite, but when i try to insert for example mega pinsir i get this and somehow i think its related to the idea that the original pinsir sprite does not have some other colors, only showing in the mega pinsir sprite, here's the difference, , i think i skipped some sort of palette modification step or something, can somebody help me pls! ive tried some tutorials but they werent so good, pls help, thank you