If you can do a full wort boil with extracts is it still beneficial to be adding extract late to avoid color changes and the like?
What would happen to hop utilization with extract late in a full boil?
Most recipes are formulated for full wort, full gravity boils. Reserving extract would increase your hop utilization and the beer would be slightly, but probably not noticeably, lighter. Make your own decision about the benefits.
if you are using brewing software a lot of them have the option of indicating that your extract is being used as a 'late kettle addition' and you can then set the time (i.e. 15m from flameout), by doing this the software should automatically adjust your SRM and IBU's.