K3[Co(NO2)6]= Yellow ⇒Co3+=3d6⇒t2g6eg0 ‌K4[Fe(CN)6]=Yellow⇒Fe2+=3d6⇒t2g6eg0 ‌K3[Fe(CN)6]=‌ Bright Red ‌⇒Fe3+=3d5⇒t2g5eg0 ‌Cu2[Fe(CN)6]=‌ Chocolate brown ‌ ‌Zn2[Fe(CN)6]=‌ White ‌ Spin only magnetic moment of complex having Yellow colour is zero.