I'm having trouble with picking and testing colors on the image because the color palette is too small for my laptop display. Is there a way I can make color palette's window bigger?
An alternative option is to open the color panel, Window -> Color.
The panel can be size to your liking but it is not convenient to change how you pick a color (HSL, Lab, Hex, Etc). To bring that up you have to select that from dropdown (3-line icon).
Just slowly hover your mouse cursor over the panel's borders until you see a double-headed arrow, click, hold and drag. I hope this will help if you are using Photoshop CC. Because earlier versions like CS6 will not support this method.