dunno, maybe you typed it wrong or something. Try gfx.getHexColor by itself
Also, gfx.getHexColor only works for lua commands like tpt.el.neut.color = , not for commands starting in !set
tpt.el.color is in AARRGGBB format. Instead of a number like 0x999999, try gfx.getHexColor(255, 0, 0, 255), where the arguments are alpha, red, blue, and green. Up to 255 for each (255 being most red, 0 being no red)
sorry for "spammy" comments
i think its just a small bug, i will restart tpt
and... again... cant change color of neut and warp(ONLY NEUT AND WARP) :tpt.el.[neut or warp].color=0x99999(random color) it change color in menu but not in save