Try to color the trail a bit

heat.cpp

@@ -60,7 +60,12 @@ void Heat::generate_path(const std::string& filename, const Date_Caches& sorted)
 
 	const Cache* prev = sorted.begin()->second;
 
+	float h = 1./3;
+	float h_step = 2./3/(sorted.size()-1);
+
 	for (auto el = sorted.begin()++; el != sorted.end(); el++) {
+		draw.push_back(Magick::DrawableStrokeColor(Magick::ColorHSL(h, 1, 0.5)));
+		h += h_step;
 		draw.push_back(Magick::DrawableLine(mp->coordinate_x(Position(el->second->pos.lat, el->second->pos.lon)), mp->coordinate_y(Position(el->second->pos.lat, el->second->pos.lon)),
 											mp->coordinate_x(Position(prev->pos.lat, prev->pos.lon)), mp->coordinate_y(Position(prev->pos.lat, prev->pos.lon))));
 		prev = el->second;