Creating GUI

 Was wondering what the ideal export criteria is for buttons on the x4 user interface. Ive made buttons in the past but could never get the size quite right. What is the best export dpi from draw and what size should they be made Ie: 22x 22 pixels exported to bmp @ 72 dpi gives me a button that is somewhere between a large and medium size button. I would like to make smaller but the resolution seems too small for anything ledgable. Whats the scoop with color now? Greyscale only????

Thanx for any help

Andy