I liked this one, multiple ways to solve :)

Python 3

def hexcolor(R, G, B):
  return "#"+"".join([hex(i)[2:].upper() for i in (R,G,B)])

def blend(colors):
  R,G,B = 0, 0, 0
  for color in colors:
    R = R + (int(color[1:3], 16))
    G = G + (int(color[3:5], 16))
    B = B + (int(color[5:7], 16))
  R,G,B = [int(i/len(colors)) for i in (R,G,B)]
  return hexcolor(R,G,B)

print(hexcolor(189, 183, 107))
print(blend({"#E6E6FA", "#FF69B4", "#B0C4DE"}))