You do not have to get them to 45F. Honestly, I wouldn;t even consider pushing them to 45F.
Blue/purple hues will show at temps 65F and less. I would not go below 58F.
Though Mr. Green Thumb may have had success in this temperature range, I feel that it is much too cold to push forth throughout flowering and expect good yields and minimal stress. Plant metabolic processes start to slow down, extremely, under temperatures of 55F.
Lastly, I have a purple maroc in flower right now and my temperatures have never gotten below 61.7F. She is showing some awesome hints of purple and lavender. I have also run many Purps; temps have never gotten below 60F in any of my grows, and I have had some of the best purple/blue hues you could ever want.
Just my two cents. If you do decide to push to 45F for color, just remember who told you not to