Calculate age in days at end of each month

[Roger_Dalomba]

Been searching for several days and can’t seem to get this calculation.
I know that in google sheets this returns days between today and end of month

=EOMONTH( TODAY() , 0) - TODAY()

I’m trying to have a conditional format
if something is 50 days old today but will be 75 days or older ——RED
Second criteria if it was purchased from a specific vendor mark YEllow at 60 days instead of 75