Although it may sound impossible - you CAN draw multicolored lines/polylines in AutoCAD.
MLINE functionality can be used for this. Use the MLSTYLE command to define a new multiline style and define (element properties) two line elements, both with the offset equal to 0. Set different colors to them (e.g. green and red). Use different linetypes, e.g. DASHED and DASHED2 (you may need to Load them first) - for real-life applications you will probably need to define your own linetypes. Save the new Mline style. Now use the MLINE command to draw a polyline using this new mlstyle - it has alternating green/red colors!
You can use the same approach to define even three or more colors.
As AutoCAD allows to define complex linetypes containing text, you can even make linetypes (mlines) with embedded text in a different color than the line (e.g. line in a BYLAYER color and text always in blue). For this you need to define one complex linetype containing text and almost no lines (e.g. only dots) plus a appropriate dashed linetype with spaces for the text. To see the principle you can define such multicolor text linetype using MLSTYLE with elements of DASHED and GAS (shipped with AutoCAD) linetypes. See the BUDWEISER benchmark drawing (DWG also downloadable from www.cadstudio.cz/download) for examples (benchmark #5).