What I would do is use a global variable that determines what sprites the character uses. Let's call it global.kid_color. Have the Player execute this code after using the warp that causes him to change color. An excerpt of how my crappy fangame in progress is coded:
if global.kid_color=0
{
s_idle=thekid_idle
s_walk=thekid_walk
s_jump=thekid_jump
s_fall=thekid_fall
}
if global.kid_color=1
{
s_idle=thekidpink_idle
s_walk=thekidpink_walk
s_jump=thekidpink_jump
s_fall=thekidpink_fall
}
sprite_index=s_idle