Well, the easiest way is to take the average value for each of the red, green, blue and alpha values:
Color c1 = ...;
Color c2 = ...;
Color midpoint = Color.FromArgb((c1.A + c2.A) / 2,
(c1.R + c2.R) / 2,
(c1.G + c2.G) / 2,
(c1.B + c2.B) / 2);
, A, R, G B , ints , . [0, 255], FromArgb Int32, , 8 - , .
(, HSV), . .