A friend in Cairns sent this pic of M. garrawaye, aka Mt white Lime. From my memory the skin is very bitter, somewhat similar to calamondin LEAF flavor, but worse.This tree's fruit had white pulp vesicles, similar to cooked white rice in texture. After eating a few, a sticky resin remained on the teeth. I haven't seen a fruit for a few years, and hesitate to describe the flavor from memory.

It is true that the peel of the Calamondin fruit is bitter ONLY IF eaten green. On the other hand, if the Calamondin fruit is ripe, has deep orange tinge, it is very soft and quite palatable with no bitterness at all, and excellent for mamalades. After all, Calamondin is a fortunella hybrid, and also has edible rinds when eaten at the proper time.

I am wondering if the skin of Mt. White Lime changes color when fully ripe and are they edible when fully ripe?

It is important to note that the Calamondin is best to use as condiment or refreshing drink, or as a cocktail mix, when the skin color is between shiny green to yellow green. In this case, the discarded peels are not good to use because they're bitter.

If the color of the peel is from yellow to dark orange, the Calamondin is better to use as marmalade.

In a way, the use of Calamondin is similar to lime, they're really good when they're green to yellow green, but not as good when they ripen. That is why, you can sometimes have misnomers like Philippine Lime which is mistakenly applied to Calamondin. There exists a real Philippine Lime, unrelated to Calamondin, but that is another story.

As mike_N says, the mature fruit is green and start falling off. My description and the photo is of such a fruit. I wouldn't really describe M. garrawae as a 'lime", wheras some M australasica "finger limes" could pass as limes.
This M.garrawae is edible and enjoyable, but probably not for sweet tooths.