Survey Form, input border change color on click

I’m doing the Survey Form and I noticed that clicking the input fields the border color change, but I didn’t understand how to do it

Your code so far

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User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0.

Challenge: Build a Survey Form

Link to the challenge:

I’m guessing you mean the sample project.
What have you tried?

Yes, sorry.
I tried :focus and change the border color but doesn’t work.

Without seeing your code all I can do is guess. Please provide a link to your project.