Proposal to apply footnote 18 to the symbol for tell-tale No. 1 (master lighting switch) in order to simplify the treatment of colour changes of tell-tales. Footnote 18 specifies "“Symbol may be shown in other colours than specified in column 5 in order to convey different meanings according to the general colour coding as proposed in paragraph 5. of ISO 2575-2004.” This proposal clarifies the existing understanding of the intent of the regulation and in particular addresses concerns over interpretation where tell-tales Nos. 1 and 19 have been combined.
43. Recalling discussions at the previous GRSG session on the handling of colour changes of controls, tell-tales and indicators, the expert from OICA presented ECE/TRANS/WP.29/GRSG/2018/6 as a long-term solution. He explained that the proposal aimed to remove the references in Table 1 to footnote 18 and to only keep the reference to standard ISO 2575:2004. GRSG noted study reservations by the experts from France and the United Kingdom. GRSG agreed to resume consideration of this subject at its next session.
49. The expert from OICA presented ECE/TRANS/WP.29/GRSG/2017/18 to clarify footnote 18 where tell-tales Nos. 1 and 19 were combined. Some experts were of the opinion that footnote 12 already offers that possibility. Following the discussion, the expert from OICA offered an alternative proposal GRSG-113-39 that simplifies the handling of colour changes of tell-tales and to remove footnote 18 and all references to it. The expert from France preferred to keep the existing text of footnote 18 and to only insert under symbol No. 1 a reference to footnote 18, as reflected in GRSG-113-42. GRSG agreed to go forward with a two-step approach and adopted ECE/TRANS/WP.29/GRSG/2017/18 as reproduced below.
| No. | Column 1 | Column 2 | Column 3 | Column 4 | Column 5 |
| Item | Symbol 2 | Function | Illumination | Colour | |
| 1. | Master lighting switch
|  1, 18 | Control | No | |
| Tell-tale 12 | Yes | Green |
50. The secretariat was requested to submit the proposal to WP.29 and AC.1 as draft Supplement 10 to the original series of amendments and Supplement 3 to the 01 series of amendments to UN Regulation No. 121 for consideration at their March 2018 sessions, subject to the endorsement of the Working Party on Lighting and Light Signalling (GRE) at its October 2017 session. (Note by the secretariat: At its seventy-eighth session, GRE endorsed the principles for amending UN Regulation No. 121 as proposed by GRSG.)
51. As a second step, GRSG requested the secretariat to distribute GRSG-113-39 with an official symbol, for consideration at the next GRSG session and to also circulate it all WP.29 Working Parties concerned.
| GRSG-113-42 | |
| GRSG/2017/18 | |
| GRSG/2018/6 |