a horse of a different color

a completely different matter in comparison to what one used to deal with

The idiom "a horse of a different color" is thought to have originated in the 17th century. It is believed to have come from the horse trade, where horses were often sold with false pedigrees. If a horse turned out to be different from what the buyer had been led to believe, it might be said to be "a horse of a different color." This idiomatic expression is used to describe something that is different from what is expected or usual.

I thought I was going to a boring lecture, but the professor's teaching style was a horse of a different color.She used interactive games and group activities to keep us engaged.
The company's usual strategy of cutting costs didn't work this time, so they had to try something different.This new approach is definitely a horse of a different color.
I was expecting a traditional meal, but the restaurant's menu was full of creative and experimental dishes.It was definitely a horse of a different color.
The politician's usual speeches are full of empty promises, but his latest address was a horse of a different color.He was more honest and transparent than usual.
I thought I knew everything about my best friend, but then she started dating someone new.He's definitely a horse of a different color from her usual type.