Hex #66d880 or rgb(102,216,128) in RGB space is the tint of bluish green. It has hue angle of 133.68 degrees, value = 85 and saturation = 53. #66d880 can be obtained by mixing 3 colors: 1 drop of cyan, 5 drops of green, 4 drops of white.
Nearest safe hex - #66cc99. Below you can see the block with #66d880 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66d880 to the mixer and play with it.