Is there any way to recolor an embeded excel graph color
to match the color scheme of PowerPoint?
Sure. Two different approaches:
Doubleclick the excel graph to launch it, then edit the colors as you would
normally in Excel.
Or
Rightclick the graph, choose Format, click the Picture tab then click Recolor
which'll give you the ability to choose several ways of mapping the Excel
colors to the PPT Scheme colors.
Or (hey, another one for free!)
Ungroup the graph to convert it to PPT shapes then use the normal PPT editing
methods to change the colors as need be.