Get aHEAD

Challenge Descriptoin

Find the flag being held on this server to get ahead of the competition

First I visited the webpage from the browser and there is two buttons which changes the background color of the page.
I opened network tab and found nothing special.
So, I opened Postman client to play with the url.
After playing with request headers for awhile I got nothing and I was clueless.
Then I did some research and understood the mystery behind the challenge name.
The name is Get aHEAD and here the part HEAD is all uppercase. So, there is something to do with this word.
Then simply I just did a HEAD request instead of GET or POST request using Postman.
And thus I got the flags in response headers