From GCAA CV regulation:
"(i) Initial Applicants for Class 1 who fail the Ishihara’s test, or
(ii) Renewal Applicants who previously passed screening test and failed the current screening testing, or
(iii) Holder of Foreign waiver at initial GCAA Medical application, or
(iv) Current holder of GCAA Medical Class 1 who had previously granted a waiver based on foreign waiver/or advance colour vision tests not approved by GCAA.
Note: Current GCAA Licence Holders who had previously passed Anomaloscopy or Lantern testing acceptable to GCAA (Holmes Wright, Beynes, or Spectrolux) are not required to take CAD test."