In the person's message box, there is a "quote" button.
Hit that and you quote their entire message.
I typically crop everything but the actual writing (just delete their comments).
And from there you have a choice of how you want to leave your comments.
There is a large "A" at the top, and near it is an arrow to change color. Hit that and change to any colore. Every time after that, you can just tap the "A" and the change will occur. Depending on your system, you might get something like [COLOR="Red" ] [/COLOR] without the space near "Red" and the ]. Anything typed {Red"] In here [/Color} will be in color.
Or, you can just hit the "B" to leave in bold. Works the same way, but with [B ] [/B]
Or, you can cut every line up with the "quote" button, but that's tedious.