Diffrent color for 1 menu item

Hello,
I would like to change the text color of 1 item in menu. I did the css for that:

.sample-tab1 a {
color: #172842;
}

I pasted the css in all 4 css custom fields (desktop, ipad and phones) and in “menus” I added the css class name “sample-tab1”. But the color of the item doesn’t change…

Can you tell me, how can I change the color of 1 item in menu?

The site url is: https://lubnianskiosrodekkultury.pl/

Hello,
I want to change the color of the item “Katalog on-line” (the color of the text). On the print screen i marked it with red, and I show you the css settings and menu settings on the screen also:

https://redit.pl/wp-content/uploads/2023/02/screen.jpg

I thought the css code should work, but it doesn’t…