Stars of different temperatures (which is a function of mass, age etc) emit different spectra. The historic "Harvard Classification Scheme" is still used to describe these differences. Here is the basic scheme:

Spect Type	Spectrum	Color	Temp (K)
O	ionized + neutral He, some H	bluish	>31x103
B	neutral He, stronger H	blue-white	9.8 to 31x103
A	strong H, ionized metals	white	7.1 to 9.8x103
F	less H, ionized metals	yellowish white	6.0 to 7.1x103
G	weak H, ionized + neutral metals	yellowish	5.3 to 6.0x103
K	v weak H, neutral metals	orange	4.0 to 5.3x103
M	none (v.v.weak) H, neutral metals, molecules	reddish	2.0 to 4.0x103
L	no H, metallic hydrides, alkalai metals	red-infrared	1.5 to 2.0x103
T	methane bands	infrared	< 103

There are many sub-classification schemes used to denote even more subtle variations (eg The Sun is a G2 star). However the details of the classification scheme & definitions are beyond the scope of the course.