This is a Dye Marking that was introduced on the Forest breed on January 31, 2014. It currently changes the color of the vines on the Forest breed, And appears as a regular marking on other breeds. You can add this marking to your waja by use of a Dye Vines.
All examples feature wajas with the marking in FF0000 (pure red). However, this marking can come in any Hex Color as well as rainbow (simply put the word "RAINBOW" in the hex field) and chrome (simply put the word "CHROME" in the hex field).