Cosmetology
A Sims Cosmetology Talent badge level determines how often they do a successful Makeover.
No badge
High chance of messing up the makeover.
Bronze
Medium chance of messing up the makeover.
Silver
Low chance of messing up the makeover.
Gold
Very rare chance of messing up the makeover.
Positive effect
A successful makeover opens the "Change Appearance" options screen. Here you can change the appearance of the Sim you did a makeover on. The customer will be pleased and if you did not offer a free one, pay you.
Negative effect
An unsuccessful makeover displeases the customer and their appearance is changed, usually a weird haircut or full face makeup. But your Sim still gets paid if it wasn't a free makeover.