A common mistake people make reading that section of the documentation Lionel pointed at is to just read the section related to the widget you are looking at. e.g. in the case of Buttons this section http://www.generomobile.com/online_documentation/fjs-fgl-manual/#r_fgl_presentation_styles_button_style_attributes.html
What you should also do is make sure you read the "Common" section which applies to all widgets and containers http://www.generomobile.com/online_documentation/fjs-fgl-manual/#r_fgl_presentation_styles_common_style_attributes.html
So you wont see backgroundColor in the Button section, you will however see it in the Common section.
As the common section applies to all widgets and containers, there are times where the blanket "Yes" should really be a Yes(*) and a note added to indicate what O/S may not support a particular feature.
If in doubt create a small example like this ...
OPEN WINDOW w WITH FORM "button"
ON ACTION red
ON ACTION orange
ON ACTION green
BUTTON b01: red, TEXT="Red", STYLE="red";
BUTTON b02: orange, TEXT="Orange", STYLE="orange";
BUTTON b03: green, TEXT="Green", STYLE="green";
<?xml version="1.0" encoding="ANSI_X3.4-1968"?>
<StyleAttribute name="backgroundColor" value="red" />
<StyleAttribute name="backgroundColor" value="orange" />
<StyleAttribute name="backgroundColor" value="green" />
... then if the program isn't doing what you expect, you can pass it your support contract, or post it here
Hope that helps,