Not long ago, I was looking for the HEX code for a specific color for which I already had the RGB numbers. So, of course, I Googled "rgb 66 78 205" thinking that, perhaps, there would be a Web site returned in the list that would allow me to enter the RGB numbers and have the HEX returned to me.
What I saw, however, was Google's color picker with my color selected along with the HEX and RGB codes off to the left.
I played around with the tool and found it to be both simple and very helpful.
Now, if you're looking for color schemes, I would still recommend taking a look at Paletton.com. Very cool and useful tool!