I think something like this is what you're after (I created some data for this example):
data = Range@20; tbl = Transpose[{data, data^3, data/25}]; ListLinePlot[tbl[[All, {1, 2}]], ColorFunction -> Function[{x, y}, Darker[ColorData["Temperature"][tbl[[Round[x], 3]]], .2]], ColorFunctionScaling -> False]

Setting the ColorFunctionScaling to False gets you the X value which is then used to index back into your data to get the desired index of the color scheme. Note that if your actual X values are not integers, you'll need to use other means (lookup, or an incrementing counter) to index into the desired color. Here's an example of that:
colors = tbl[[All, 3]]l cnt = 1; ListLinePlot[tbl[[All, {1, 2}]], ColorFunction -> Function[{x, y}, Darker[ColorData["Temperature"][colors[[cnt++]]], .2]]]