Region Transparent Background

setHighlightTextStyle (bgColor, textColor, textSize)
ankulua.boards.net/thread/6/objects-methods-introduction-sikuli-compatible#highlight

The color formats are in ARGB format.
When A is 255 (0xff in hex), it's transparent.
For example, the following settings will make background transparent and black text.
setHighlightTextStyle(0x000000, 0xff000000, size)