This can be handy for any sewing/embroidery/overlockers(sergers). Not everyone thinks about it & they just go & pull all the thread from the top, wind it back on the reel/spool... Then have to re-thread the whole machine again from the start. I learnt this when I was working at an embroidery business many, many years ago.

Now.... Instead of taking all the thread off the top of the machine, leave it right where it is. Cut the thread at the reel/spool with enough thread to be able to tie your new colour to. Place new thread onto holder, tie a tight knot of the old & the new threads. Trim the excess tail after the knot off, leaving about 1/2" tail. Now from the needle end, take the thread out of the needle & pull that part of the thread through until the new thread is all the way to the needle & just cut the old thread off. All you need to do now is thread the needle & away you go. I use this method ALL THE TIME on any machine. Just pull the thread through slowly & it won't break, you may need to give a small tug in one point.... this will NOT hurt your machine.
I know what it's like to be changing threads back & forwards as I have been doing it on machine embroidery for at least 25yrs, so ANY short cuts we can use in our sewing, etc. Go for it, you will find it becomes more of a pleasure to change a thread easily from now on.
Reggie