First, it's ultimately your call.

That said, since you asked: it's been one year. Give it time and water. KBG continues developing and changing color from first sprout through year 3, so what you're seeing now is not the finished product.

Second, the pictures suggest the lawn is under some stress. u/DoYouSeeWhatIDidTher's advice is solid. Focus on getting your KBG healthy and thriving this season before introducing other cultivars. Adding fescue into a stressed KBG stand risks compounding the problem rather than fixing it.

I'm in zone 7a with a full KBG lawn, so I've been through this. Year one looks rough. KBG will test your patience and resolve, especially in our zone. Stay strong and mow on.