color-coded reference marking

col·or-co·ded re·fer·ence mark·ing

(kŏ'lŏr-kō'dĕd ref'ĕr-ĕns mahrk'ing)
Colored band on the World Health Organization probe located 3.5-5.5 mm from the probe tip, used when examining using the Periodontal Screening and Recording System.