Rock coloring

Why does some rock appear much much darker, say a deep driftwood brown. My rock is almost white. It's live but i'm not sure from where. I have two large fiji boulders and they're all sorts of colorful. Does rock get any extra color as it ages in the tank environment?

 

you can have all different colors at 1st.sometimes it will turn green or brown before purple or pink,but eventually most if not all will become pink or purple.

 

it depends on what was on it in the ocean. For example, my rock has a lot of white because it used to have coraline algae on it, but it had died at some point. It now has some small specks of purple, which i hope is coraline, and lots of green from algae. The actual color of my rock is a greyish sort of color. I really think it depends not only on the area taken from, but also what is is made of.

 

i have a rock that i bought from a coral tank just for the coraline on it. it has lime green,dark red,purple,pink,and some purple coraline the grew up off the rock in branching form(for got what this is called) anyways it was cool still is. except it kinda got some brown algae on it,and some bleaching on it, from my old tank, but its slowly coming back in the new tank.

coraline comes in many shapes and colors . and you can distinguish it from a sponge or bad algae by rubbing it. coraline is like rock hard.
the brown is just diatoms or just aged color. white is old dead coraline that bleached out, or also the start of new coraline

 

sweet, that sounds like the two large fiji's I got. I really hope that starts to spread out in the next few months. Thanks for all the input.