Have a look at the GetGridColor Method in the ActiveX (vba) reference
gridLineType
AcGridLineType enum; the type of the grid line
acHorzBottom
Top or bottom horizontal grid line, based on the flow direction.
acHorzInside
All horizontal grid lines, excluding the top and bottom lines.
acHorzTop
Top or bottom horizontal grid line, based on the flow direction.
acInvalidGridLine
An invalid grid line.
acVertInside
All the vertical grid lines, excluding the farthest left and farthest right grid lines.
acVertLeft
Farthest left grid line.
acVertRight
Farthest right grid line.
rowType
AcRowType enum; the row type
acDataRow
acHeaderRow
acTitleRow
acUnknownRow