No, if you try to manually set the color with the PaintBucket tool, you’ll see the cursor change to a not allowed cursor over the Guide line. Also if you select the guide and look at the Entity Info panel, you’ll see that there are no material swatches.
So in reality, the API should have removed the #material and #material= methods from the ConstructionLine and ConstructionPoint subclasses. (We might consider it an API Issue.)
The only way I have found to have different guide colors is to have the guide assigned to use different tags (layers) that have differing colors and then use the Color By Tag rendering option.