I pieced together the following code from other StackOverflow articles that solved similar problems.
Dim light As MsoRGBType, dark As MsoRGBType
light = RGB(195, 214, 155)
dark = RGB(79, 98, 40)
ws.Shapes("Arrow1").Fill.ForeColor.RGB = dark
In the last line of code, I get the error:
Runtime Error '-2147024809 (80070057)': The value is out of range.
Fetching the shape does not throw the error, I checked that. I cannot ascertain Excel's native way of setting shape colors because, strangely enough, recording the manual changing process produces an empty macro.
The shapes I am working with are standard lines with arrow-style endpoints, in case that is relevant to the coloring process.