For about a decade now, I have used TrayColor as a must-have utility to pick colors off the screen and get their HEX for html and css. It’s tiny, works perfectly, sits in the tray. It’s few quirks seemed to be minor enough and it was free. I don’t know who made it. I used to get it off a site called Spinning Jenny, but that seems to be gone.
I just tried this alternate program from Veign called Pixeur. It’s also free and also sits in the tray. It’s a bigger program but not huge and it launches as quickly as TrayColor. It adds a few features, like a larger preview window so I can really target a specific pixel color, like a 1px border. It also gives you the ability to save colors and see a theme of matched colors for a palette. These little extras make me want to give it a go. Plus the little quirks from TrayColor aren’t there. Like I can double-click the icon in the tray and it pops up.
So far it’s nice, I give it a good rating. Give it a try.