well the original 青comes from a dye called 靛青(indigo-blue)，later 青 can be used for describing those colors： 1. blue：青天means blue sky; 2. indigo blue：靛青 3. deep green：青草；青山； 4.black：青衫（black clothes） I think 绿水 is easy to understand，：D river around the mountain if not polluted always shows green color，：D

green hills and blue waters here it means beautiful sceneries

Here,“青山绿水”means all the beatyful scenery风景

Blue mountains, green waters, usually expressed beautiful scenery.

在這句句子中，青山綠水沒有太大的特殊意思！只是用來表達沿途的風景很漂亮的一種描述的手法而已！