Main Sequence Spectral Types, Temperatures and B-V Color Indices (Data in red pertain to brown dwarfs and are somewhat uncertain.)
Spectral Type	Temperature [K}	B-V
O5	42 000	-0.33
O9	34 000	-0.31
B0	30 000	-0.30
B2	20 900	-0.24
B5	15 200	-0.17
B8	11 400	-0.11
A0	9 790	-0.02
A2	9 000	0.05
A5	8 180	0.15
F0	7 300	0.30
F2	7 000	0.35
F5	6 650	0.44
F8	6 250	0.52
G0	5 940	0.58
G2	5 790	0.63
G5	5 560	0.68
G8	5 310	0.74
K0	5 150	0.81
K2	4 830	0.91
K5	4 410	1.15
M0	3 840	1.40
M2	3 170	1.49
M5	3 170	1.64
M8	2 800
L0	2 450
L1	2 300
L3	2 000
L5	1 680
L7	1 520
L8	1 400
T2	1 320
T6	1 020
T7	900
T8	800