Converting from RGB ints to Hex

Using string interpolation, this can be written as:

$"{r:X2}{g:X2}{b:X2}"

Try the below:

using System.Drawing;
Color myColor = Color.FromArgb(255, 181, 178);
string hex = myColor.R.ToString("X2") + myColor.G.ToString("X2") + myColor.B.ToString("X2");