Choosing a color palette for OOo is quite a tough challenge, 12 shades of gray is a lot, 7/8 is the limit of what you can distinguish "easily". So I tried a pragmatic approach, with shades of gray from 25% to 90%, a first row of 6 colors sticking to 10 multiples, and a second one with multiples of 5. Then setting saturation to 100% (assuming vibrant colors are the best to draw charts), there's only the hue left to play with. So aesthetically speaking, it's, hum, perfectible. Slight gradient to darker colors somehow improve the results.

Anyway, IMO, the best way to make colors stand-out on any background are outlines (I like thick rounded outlines, but it gives a cartoonesque look which might be inappropriate). Inverse video is also very efficient, but not always nice to the eyes. Yet another solution is to associate two colors, one for the fill and another one for the outline so your chances of confusion are lowered (2 hints instead of 1). Or to associate motifs to colors (stripes, bubbles, stars), but this does not work for lines.

Anyway, here's a first try