If Mono got sth from last night, there has to be a player who checked Reborn that phase, too. It‘s not on the WU associated with a character/flavour, so if somebody did, they can reveal. But if not Mono might just be lying here.
If I am getting this right then there are two options here
First,
Lucci stole Ace invest
Lucci investigated me and got result
Monochrome color got result too
Second,
Monochrome is Lucci
And, came out in open that he got result on me
Problem with second option is that it doesn't make sense as gameplay
MC wasn't a sus and not under any pressure to come out to reveal this info to gain town cred. He doesn't need to do anything to gain town cred as no one was sussing him
As scum his best bet would be to withhold this info instead of town clearing me