I only had to take a proper colour test twice both whilst seeking employment with Plymouth Dockyard and a few weeks later with Cable and Wireless in 1975.
They took the form of numbers hidden within the patterns of irregular blobs of colour.
The first 10 or so were primary colours and easy to spot but as the cards went on the colour changes became more and more subtle.
ISTR you had to score over 95 out of 100 cards.
The 70's were indeed golden years for opportunities I went to a dozen interviews as well as the above including Mullard and NCR in Southampton, Texas Instruments and Bush in Plymouth and of Course Plessey Avionics and Communication in West Leigh Hampshire (where I ended up).
I was unable to get any opportunities in the Radio and TV trade in East Cornwall. The Liskeard area was awash with Radio and TV sales and repair companies and sole traders all fighting over an already shrinking market or so it seemed. I had even worked for a couple of them Saturday jobs some 3 years earlier.
My hit rate was pretty good only one non offer (Bush, overqualified apparently for the role on offer).
Then Moved to Plessey controls as a Field Service Engineer in 1978 the freedom was immense but I now look back on it and wonder how I survived
So to me the 70's and the 80's when I started my overseas career first Port Elizabeth SA, then Hong Kong were the most exciting times for a young FS guy with the world before him.
Cheers
Mike T