1) from RGB to Hex value
Put RGB values into the text field R, G, and B. Leave the mouse into the one of text fields. And hit the return key. RGB values must be between 0 to 255.

2) from Hex to RGB value

Put Hex value into the text field Hex. Hex value must be 6 digits of "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F". Leave the mouse into the text field Hex. And hit the return key.