Lost colour on transfer?

[silverfoxcc]

Copying Digital 8 tape onto a extl HDD

When i play them back , a lot, but not all, of the clips are now in grey scale mostly the one of preserved steam locos

Any idea as to why this has happened and any ideas on how to recover the colour?
Although i have not viewed the HDD copies for some time ,i am sure that they were in full colour the last time i viewed them