Coloring gauge and coloring inspection method for runner surface at inner coating of compressor casing

The invention discloses a coloring gauge and a coloring inspection method for a runner surface at an inner coating of a compressor casing. The coloring gauge comprises a positioning bushing and a pluggauge, wherein the positioning bushing is used for being positioned and installed on the end face of the input end of the compressor casing, and the plug gauge is installed on the positioning bushingand used for stretching into the inner runner face of the compressor casing from the input end of the compressor casing for coloring inspection. The positioning bush is provided with a first reference surface used for being matched and attached to the end face of the input end of the compressor casing. The measuring end of the plug gauge is provided with a coloring surface which is matched with the standard runner surface and is used for coating a coloring agent; the mounting end of the plug gauge is mounted on the positioning bushing; the relative position relation between the coloring surface and the first reference