Heres a few Colour schemes from Mini-maps i've seen around EAs campaigns.Your more than welcome to use these to guide your way through making your own mini map.

Things to watch out for

you will need to use your own border style for the edges of different terrain, as I cannot accurately Pin them to one specific colour.

Yuriko's mini map has details from the map coloured in white(large objects like beds and boxes,ect) you will need to use a border of pure white to show corridors and faded white for details on the floor.

you will need to add a shrinked text to look like data, and maybe an odd symbol faded off map somewhere on the grid.

note the overlay is Opacity just incase your confused. if its not 20% for example then it will be the remainer aka 80% as most of the fadings are very tranparent.

Enjoy!

Use blue only for the background, Use white for everything else(in approrite fade,details only).