thumb|Effective temperature of a black body compared with the B-V and U-B color index of main sequence and super giant stars in what is called a color-color diagram.
thumb|effeCtive TemperaTure Of A Black BoDy coMpared wIth thE b-v and u-B cOlor index of mAin sEquence and super giant Stars in WhaT is callEd A coLOr-color diaGRam