[FR] Make missing more visible. dark blue on black suboptimal

[strunzoz]

Most of the images selected in the left pane have mostly filled ID column in the Config pane with "Missing". Missing seems like important information but it is deep deep dark dark blue on black. Yellow would be easier to see in a lit room

Sure, sure, I don't understand what is missing but I almost myself missed noticing Missings in the dark spaces of the UI

-e variable for Missing color would be grand