Specific colours for folders?

I have already followed all the steps to change the colour of my folders, and I am at the step where I have my folder in preview and have the Adjust Colour window up.

I don't know if I am missing something, but is there a colour dropper? Or is the only way to adjust the colour is by using these sliders? I am trying to get the colour with hex code #4b528b (among others) but there isn't an option for hex codes either from what I have seen.

If I were just wanting the folder to be an unspecific colour this would be fine but I am wanting to give each folder a different specific colour (I would like them to match my background) which is extremely difficult and time consuming if these sliders is the only way. Thanks.