The fall damage multiplier attribute has coloring opposite of what is expected when applied on an item.
How to reproduce:
Give yourself an item with the attribute applied on it:
/give @s brick[minecraft:attribute_modifiers={modifiers:[{type:"minecraft:generic.fall_damage_multiplier",name:"a",operation:"add_value",amount:-0.5,uuid:[I;1,1,1,1],slot:"mainhand"}]}]Notice that the attribute description is red despite it having the positive effect of reducing fall damage.
I don't think -0.5 is meant to be a valid value, I believe that attribute is defined to be min 0.0 & max 100.0. If -0.5 is not failing, a separate bug to be filed?
What color is +0.5?