Changing the color of chosen graph lines in Excel

[lavov]

Hello everybody!
Does anybody knows how to solve this proble in Excel (2007). I have to draw two graph-lines with same color for one characteristic value α, all on one graph (like shown in picture one)!. For example, I want both graphs with α=10 (but different values of Xi/H) to have the same color (dark blue). When Im drawing second α=10 graph (lower one), I have to choose new data, and when I do this, new graph is shown but in new lighter color (picture 2). Maybe I could solve this problem by manually changing the color of lower graph to dark blue, but i dont know how to do it? I hope I made my self clear.

[Andy Pope]

Select to line.
CTRL+1 to display format dialog.
Line Style and pick the required colour