wanted to add as much of the DME at the end [...]
This
article (link) has a process outline for brewing with almost all the extract added at the end of the boil. The last paragraph covers hop adjustments. I've used the process once or twice. The process produces good beer.
@D.B.Moody 's process (link in #2 above) is a nice refinement on the traditional "partial boil with late additions of extract" approach.
How to Brew, 4e (2017), in the 1st 9 chapters of the book, is a good source of addition information on the basic process. (There are still a couple of things in the book that still have not made it into "forum wisdom").
wanted to add as much of the DME at the end to keep it light.
When I brew a 'traditional' recipe with DME, my process is add all the DME before the start of the boil (typically at 140F if no steeping grains are involved, otherwise 160F) then do a 30 min low intensity boil (
indirect link to visual reference).
I have measured the wort color at the start and at the end of the boil. It doesn't darken much (1-ish SRM). I suspect that DME, properly added and boiled, darkens at about the same rate as an all-grain wort but have not done the measurements.
(eta: I have very little experience with LME. Discussion across the active forums is pretty negative on it. I suspect there are brewers that have source(s) for fresh (properly stored and shipped, aka their LHBS) LME. But they may not have a compelling reason to share their experiences.
With the claims of "extract darker than expected", one probably needs to know
- the color of the wort at the start of the boil ,
- the color of the wort at the end of the boil,
- the boil intensity, and
- how the extract was added to the kettle.
Otherwise the reports probably contain insufficient information to troubleshoot the problem.
Stale LME is a likely primary cause of most 'extract darker than expected' reports. If the LME starts the boil as an SRM 12 wort in the kettle, adding half at the end of the boil won't create an SRM 4 wort.
Secondary causes (indirect link to recent discussion) may include boiling too hard and improper mixing (resulting in either scorching or a layer of concentrated wort at the bottom of the kettle). It may be that adding all the DME late is a 'work-around' for these situations. On the other hand, a "proper boil" is one of the "top priorities" for making good beer.