how can i put a diferente colour in a grid line

You may use DynamicForeColor and DynamicBackColor of the Column. To highlite each the second line you may use following code:

THIS.setall("Dynamicbackcolor", "IIF(RECNO()%2=0,RGB(255,255,0),RGB(192,192,192))","Column")

in Grid.Init method code.

thanks very much, for the topics. What i want is to change the color of the line numer p.e. 100.

You can also use ICASE() instead of IF() for more choices
ICASE(logical1,color1,logical2,color2,...,colorn)

Or you can call a function that returns a color.
CategoryColor(query.category)