Nikon D300 User Manual page 158

The WB Button
At settings other than K ([Choose color temp.]) and L ([Preset
manual]), the WB button can be used to fine-tune white balance on
the amber (A)–blue (B) axis (pg. 130; to fine-tune white balance
when K or L is selected, use the shooting menu as described on
page 129). Six settings in both directions are available; each
increment is equivalent to about 5 mired (pg. 131). Press the WB
button and rotate the sub-command dial until the desired value is
displayed in the control panel. Rotating the sub-command dial to
the left increases the amount of amber (A). Rotating the sub-
command dial to the right increases the amount of blue (B). At
settings other than 0, a E icon appears in the control panel.
r
WB button
132
Sub-command
dial
Control panel