Hot Wheels Redline Rolls Royce Silver Shadow.
The story goes, that while Rolls Royce were delighted that yet another toy manufacturer decided to model one of their fine automobiles, they were aghast when they found out Mattel had used their 'garish' rainbow of colours on their stately saloon. RR called Mattel and told them they will pull all their support from the project unless the Silver Shadow was painted in grey or grey with a black roof. Apparently, Hot Wheels abruptly halted all other colours from this casting. Whether or not that story is entirely or partially true would explain why it is rather difficult to find this model in colours other than grey, and most likely why this model was in the lineup for one year only -1969.
Like with most other Hot Wheels models from the 'spectraflame' paint era, this model was not found in all shades. The rarest colours the Silver Shadow was painted are purple, and olive. I happen to have the more common (if you can call any of them common on this model) colours of blue and green, along with the ever popular grey. Red was a bit harder to come by, but nowhere near impossible.
Many (but not all) colours were also available with a black painted roof.