At dawn and dusk, large amount of blue and violet light(shorter wavelength) has been scattered so, the light that is recieved by an observer is mostly of a longer wavelength and therefore appears to be red.
Yes, a physical quantity can have magnitude and direction but still be a scalar if it doesn't obey the vector addition. An example is Electric Current which has magnitude and a fixed direction, but it does not follow vector laws of addition.
The Rh factor(the Rhesus factor or Rh antigen), is a protein that can be found on the surface of red blood cells. It is one of the most important blood group systems in human blood typing. The presence or absence of the Rh factor is denoted as either Rh-positive (+) or Rh-negative (-).
If vectors are arranged as trigonal planar and have equal magnitude, it is an ideal case of zero resultant.
