I've a brand new in the sealed GM bag CTS .... can't remember what car it was bought for but the pt no is 90510183 
and it's blue 
Older square type blue plug
Vauxhall / Opel
Astra E (85-92)
C14NZ, C16LZ, C16NZ, E16NZ, 18E, 18SE, C18NE, C18NT, C18NZ,
E18NV, S18NV, 20NE, 20SEH, 20SER, 20XE, C20NE, C20XE
Astra F (93-98)
14SE, C14NZ, C14SE, X14NZ, X14XE, 16LZ2, 16NZ2, 16NZR,
C16NZ, X16SZ, X16SZR, C16SE, X16XEL, C18NZ, C20NE
Calibra (89-97)
C20NE, C20XE, C20LET, C25XE, X25XE
Carlton (87-93)
18NV, 18SEH, 18SV, E18NVR, S18NV, 20SE, C20NE,
C24NE, C26NE, 30NE, C30LE, C30SE, C20SE, 23DTR, 23YD, 23YDT
Cavalier II (85-89)
18E, 18SE, C18NE, E18NV, S18NV, 20NE, C20NE, 20SEH
Cavalier III (89-95)
C16LZ2, C16NZ, C16NZ2, E16NZ, X16SZ,
C18NZ, 20NE, 20SEH, 20XE, C20NE, C20XE, C20LET, C25XE
Corsa B (93-01)
12NZ, C12NZ, X12SZ, C14NZ,
X14SZ, C14SE, X14XE, C16XE, X16XE
Frontera A (92-98)
C20NE, X20SE, X22XE, C24NE
Nova (83-92)
C12NZ, C14NZ, C14SE, C16SE, C16NZ, E16SE
Omega (94-03)
20SE, X20SE, X25XE, X30XE
Senator (88-94)
C26NE, C30LE, C30NE, C30SE
Sintra (97-99)
X22DTH
Tigra A (93-02)
X14XE, X16XE
Vectra B (95-02)
16LZ2, X16SZR, X16XEL, 20NEJ