How could I change color, skin of an object when playing the game...
Is it possible in the engine right now?
Thanks for any helps

Add your skins in MED(model editor).
Ingame when you want to see a skin on a model,just enter its number

my.skin = 1;//displays first skin

similarly this will display skin 5

my.skin = 5;

Another method is to assign a material to the model.
Then adjust material parameter's rgb values.

For more info and details read the manual !

You can read the chapter on Materials in the latest manual.
A material definition looks like this :-

material mat_smaragd
{
ambient_blue = 100;
ambient_green = 255;
ambient_red = 100;
diffuse_blue = 0;
diffuse_green = 100;
diffuse_blue = 0;
specular_blue = 255;
specular_green = 255;
specular_red = 255;
power = 10;
}

then it can be assigned to an entity like :-

...
my.material = mat_smaragd;
....

You can download "MatsEd2" from my signature, it´s a material editor. It will write out the material as script, so you can copy and paste it in your code. Atm MatsEd works only with models with only one skin and no groups. But a default model is included.

Beside materials you can use self illumination:

action colour_me
{
my.red = 255;
my.green = 255;
my.blue = 0;
// yellow colour
my.light = on;
my.lightrange = 0;
}

Self illumination is not a dynamic light. You can illuminate as much as entities as you need.