Gotcha! Simple enough!

That Red wire has been replaced. Normally it would be pink from the sending unit. When the pink wire ages, it can look orange. Does the red go to the sending unit or is it spliced somewhere to the one you think is yellow? Does the yellow connect to the center of the sending unit?

Its best not to use a red wire for that because it causes confusion since red is usually +12v supply(unswitched). Once people start "fixing" wiring, they tend to buy a spool of red and a spool of black and thoroughly confuse future owners....I will admit to nothing! ;)

or one spool of red, run two wires and put a piece of black tape on each end of the neg wire

i also will admit to nothing