You will have to do a colour blindness test,thats for all applicants,but if you are applying for a Mechanical apprenticeship,it will not matter if you colour blind,as it is a requirement for Avionic Engineers to be able to differentiate different coloured wiring,etc.
So unless you wear Coke bottles,and cant see past the end of your nose,you will be ok.It is just a medical requirement thats all.There are plenty of Engineers(and pilots) who wear glasses.It is just a fact of life.