Decks, Patios, Porches and Docks - Help with Concrete - I'm repairing my flagstone patio - what to use?

I moved into a house with a patio made of flat flagstones that have concrete "grout" between them. It was greenish-black, but I recently pressure washed it and the stones are clean and the concrete is now white to off white (light beige). As I pressure washed, some of the concrete came off (as was expected because there were areas of missing concrete where it had cracked and popped out). Probably from water or general deterioation--needless to say, it needs patching.

So I want to mix up some concrete and fill in the spaces between the flagstones. I bought some Quickrete topping sand/concrete mix at the Depot. Will this match the color of the concrete there? Is there something better to be using? Some people mentioned mixing the Quickrete with sand or with lime. I've also heard I should be using Quickrete Masonry Mix. Both indicate they are good for flagstone pathways. Help!

Also, should I mix it up and spread it in with a pointing trowel, or put the dry powder in the cracks and spray it down with water?

Will this match the color of the concrete there?

Mix up a small amount and find out. Keep it slightly moist for the first day of curing. After a few days flush it off, note the wet colour; let dry, note the dry colour.

You can put an aged colour and texture into fresh cement by rubbing soil over it while still soft.