Backlight on a DMM Possible?

[Albinoni]

I've got two meters one being a Fluke and the other being a Taiwanese digital thermometer meter with all the bells and whistles. Now non of these have a backlight. I have a clamp meter which has got a backlight and that stays on for say 5 secs before going off. What I would like to know if it's possible to put a backlight in both my meters. Also both meters use a 9V battery.

Questions

1. If this can be done than can I use a button on the Meter (eg the HOLD)
button to act as a two way switch i.e HOLD and for Backlight.

2. For a LCD screen whats the best colour backlight to use ?

3. If the meter uses a 9V battery does this mean I need a backlight to
handle 9V.

Thanks