I'm already planning for a 2019 trip with my wife. I'd like to take her in the Fall to see some colors. What areas of the Q or BWCA have the best color?

It’s all beautiful, but along the north shore, and up the Gunflint is pretty spectacular. I like the last full week of September as a “general” rule...

AmarilloJim: "I'm already planning for a 2019 trip with my wife. I'd like to take her in the Fall to see some colors. What areas of the Q or BWCA have the best color?"

The area between Isabella and the north shore on the back logging roads are very pretty, and are usually at their best the first 10 days of October.
If cruising, go from Isabella to the Trestle Inn and ask for directions how to get to the Kramer (Cramer??) road and take it over to highway 61, coming out just before the Kiosk in Schroeder.
It has some of the nicest scenery in the area, including a long stretch of nothing but Maple and Oak that hangs over the road.

We will be doing a week long canoe trip. Her first and only trip was more a base camp type trip. I told her I would introduce her to some portages (LOL).

I did the Pine, Pikes area one year around first of October and thought it was pretty nice.

I guess I thought I'd see more on my 40 day trip in 2012. It ended the 28th of September and they were just starting. Like TGO said, first couple weeks in October. I like it when they are changing good yet still have pockets of green. I think it was around the 15th of October once we had a special hunt. During that hunt the leaves were spectacular... So much so, I wondered if wearing blaze orange made any difference at all.

The MN DNR site map shows the border area peaking before the majority of the park but their dates are mid Sep to early Oct. I think most of us would put that back a couple weeks and I suspect the trend is continuing. The worst risk I have faced shooting for a fall trip with color is weather with sunny periods in the 70's and higher and snow storms with temps in the 30's. I personally have forgone the search for color and try to plan my fall trips around Fall wing. What a great place to final stage before heading into the wilderness and while I might see less color, the weather is still a bit more stable.
As to where, I would go with the border lakes off the Gunflint. But for a first wife trip I might do the driving trip to see leaves, at least dry and warm if the weather is not also perfect. A fall trip is a great time of year for her to meet the BWCA.

The Great Outdoors: "The area between Isabella and the north shore on the back logging roads are very pretty, and are usually at their best the first 10 days of October.
If cruising, go from Isabella to the Trestle Inn and ask for directions how to get to the Kramer (Cramer??) road and take it over to highway 61, coming out just before the Kiosk in Schroeder."

If the bridge over the Temperance River is open, I would continue on FR166, through the Heartbreak Ridge area, to the Sawbill Trail (Co 2).

Had great colors last year in northern Quetico the last few days of September and beginning of October. The change is coming later every year it seems...

I don't think color change comes later as a rule since certain things are constant in nature.
Length of day dictates many things, such as fur priming up on animals, Mink, Fisher, Fox, Beaver, etc, and Moose & Deer antlers forming
This is the same for leaves turning color, however the amount of rainfall received can at times alter it a bit.