There are many different kinds of technical workers. Those who have learnt their skills 'on the job' (trained by the company they work for) are usually referred to as blue-collar workers. Those who have attended a college or training school and have a diploma or degree are today referred to as grey-collar workers. Technical workers can be computer technicians, electricians, airconditioning engineers, heating installers, maintenance engineers there are so many!

Blue/White *collar* worker. In reference the the colour of the work-shirt each wears (you will definitely see the collar).