Understanding systemd-analyze critical-chain output

When I run the systemd-analyze critical-chain I get output that has lines that are in red. What does that mean? And if it is part of my slower than expected boot times, what do I do to correct them?
systemd-analyze critical-chain  127 ✘
The time when unit became active or started is printed after the “@” character.
The time the unit took to start is printed after the “+” character.

graphical.target @2.325s
└─multi-user.target @2.325s
└─ModemManager.service @2.072s +252ms
└─polkit.service @1.617s +453ms
└─basic.target @1.577s
└─sockets.target @1.577s
└─dbus.socket @1.577s
└─sysinit.target @1.557s
└─systemd-backlight@backlight:intel_backlight.service @3.890s +28ms
└─system-systemd\x2dbacklight.slice @2.400s
└─system.slice @399ms
└─-.slice @399 ms
modemmanager polkit and systemd-backlight@backlight:intel_backlight.service are in red on the output.

modemmanager is disposable unless you use a phone/dial-up connection.
But you need polkit.

Awesome. I will look up how to do that.
What about the systemd-backlight@backlight:intel… ? It is red on the output and then is listed again in a slightly different way. Is the line in red going to intel for a backlight driver or something?

BTW, the backlight keys function is working fine.