The portion of the electromagnetic spectrum we can see with the human eye, longwave radiation appears while shortwave radiation appears

red , violet

Explanation:

The Electromagnetic spectrum involves gamma rays , X rays, ultra violet rays, visible rays, infrared rays, micro waves and radio waves which are arranged in order of increasing wavelength and decreasing frequency.  

Visible region is the portion of the electromagnetic spectrum we can see with the human eye. It comprises of VIBGYOR with violet , indigo, blue, green, yellow , orange and red colours. They are arranged in order of increasing wavelength and decreasing frequency.  

Shortwave radiations are radiations with shorter wavelengths and longwave radiations are radiations with longer wavelengths.

Thus longwave radiation appears red  while shortwave radiation appears violet.