Holy Crap...I think just tumbled upon a possible fix for the aggressive yellow tone on the iPhone X screen (with True Tone ON) !!! This is no joke. Try this. Go to Settings > Display & Brightness > Night Shift and slide the Colour Temperature slider all the way to the left (‘less warm’). The Night Shift setting btw is still OFF. On my phone the screen immediately turned a normal colour...the way it is on my iPhone 8 Plus with True Tone ON. No extreme yellow tone anymore. It looks like somehow the ‘colour temperature’ setting was activate even with Night Shift OFF!!! Try it and let us know... Btw can’t get the old yellow screen back anymore whatever I try now using the slider. Weird issue but very glad to have a normal and great looking screen again!