Utility Marking Colour Codes on Site

What are utility marking colour codes?

Utility marking colour codes are an agreed set of paint colours that tell everyone on site which class of buried service runs beneath a mark. The best-known scheme is the American Public Works Association (APWA) Uniform Color Code, built on ANSI Z535.1 safety colours and adopted far beyond the United States. Two colours belong to the planners, not the owners: white outlines the proposed excavation, and pink marks temporary survey points.

A shared code gives speed and consistency. An excavator operator should know, without opening a drawing, that orange dashes are telecom ducts and red ones a live cable. That shared reading is the first step in avoiding conflicts with underground utilities.

What does each colour mean?

Each colour stands for a class of service, not an owner, and the paint on the road is not the colour of the duct in the ground. The table adds typical Indian examples and the UK NJUG duct colours, since many contractors work across both.

Paint marks show plan position only; for congested junctions a grid scan and a drawing say far more. Our note 3d GPR vs 2d GPR explains when to scan a full grid instead of single lines.

Is there an Indian standard for utility marking colour codes?

No single national code governs utility marks on Indian roads, so most projects write the APWA colours into the contract or method statement. Coordination between excavators and asset owners has improved since the Department of Telecommunications launched the Call Before u Dig (CBuD) system for notifying owners before digging. IRC:98-2011 covers where services sit within urban road space, not how marks are painted.

Duct colours in India also vary by owner, supplier and decade, and many old cables were laid with no duct at all. Existing utility ducts give a clue, never an identification.

How should a utility mark be painted?

Paint over the centre of the service at regular intervals, label type, size and depth, and add offset marks wherever the centreline mark will be destroyed. Common Ground Alliance guidance describes marks about 300–450 mm long and 25 mm wide, spaced roughly 1.2 to 15 m apart, closer at bends, tees and junctions.

• Single service: dashes over the centreline, with an arrow where it turns.
• Ducts together: marks at the outer edges, with the count and size between them, such as "4 × 40 mm".
• Offset marks: on a kerb, wall or pole, with direction and distance, because the road over a trench is cut first.
• No-conflict marks: a flag stating that a checked area holds nothing, so it is not assumed unchecked.

Depth labels are written from the surface level on the day and stay estimates until the service is exposed; the reasons are in the Mezux guide: GPR Depth Accuracy.

Paint, flags or pegs: which marking lasts?

Paint suits hard surfaces and flags or pegs suit soil, but no field mark survives long, so a coordinated drawing is the real record. Aerosol paint on asphalt lasts days to a few weeks under traffic, less in monsoon rain. Decorative or heritage paving takes water-based paint or chalk with permission, while flags get pulled out and pegs are lost to mowers and cattle.

Each mark is photographed and coordinated, so it can be repainted from the utility maps if it fades. Before digging inside the tolerance zone of a marked line, expose it by hand or by suction; read Vacuum Excavation (Potholing) for the safe method.

Hand the marks over in person

A short joint walk with the excavation supervisor, drawing in hand, turns paint into shared knowledge. Doubtful sections are explained and a handover sheet is signed. If digging has not started within the agreed period, or the road has been resurfaced, the marks are checked and refreshed first.

Which marking mistakes lead to utility strikes?

Mixed conventions, trust in duct colour, faded or moved marks, and lines marked without a confidence grade all lead to accidental utility strikes.

1. Mixed conventions: a crew used to UK street-lighting orange may read an orange mark differently, so the drawing legend names the scheme.
2. Owner colours: some owners paint their own, so one scheme is agreed per site.
3. Faded or moved marks: repainted from coordinates, never from memory.
4. No confidence grade: a firm red line looks the same whether two methods agreed or one weak echo suggested it, so a quality level note is added.
5. Unknown anomalies: still marked, in a neutral colour labelled "unknown".

Confidence grading comes from subsurface utility engineering practice; see SUE survey explained simply. For how a doubtful anomaly looks on ground penetrating radar, a short guide on GPR Radargram Library pages shows annotated examples.

What does a marked-out GPR survey cost?

Ground marking is done during the scan at our standard GPR rates: ₹24 per metre for a standard drawing, ₹32 per metre with an L-section, GST extra. The minimum order is ₹50,000 in Delhi NCR and ₹1,00,000 outside it. Orders past 100 km take 25% off the whole value, past 500 km 40%, and past 1,000 km 50%. NCR mark-outs start the day you book or the working day after. Elsewhere, our operator living in your city starts at once or within 1 working day, and mobilisation or travel, if applicable, shows in the quote. If you want a particular colour scheme or label format, tell us at the start and you can plan a survey with us around it.

Sources

1. American Public Works Association, “Uniform Color Code” (ANSI Z535.1 safety colours for temporary marking). www.apwa.org
2. Common Ground Alliance, Best Practices, Appendix B “Uniform Color Code and Marking Guidelines” (mark size, spacing, offsets, no-conflict marks). www.bluestakes.org
3. National Joint Utilities Group, “Guidelines on the Positioning and Colour Coding of Underground Utilities’ Apparatus”, Volume 1, Issue 8 (2013). www.essexdesignguide.co.uk
4. Department of Telecommunications, Government of India, “Call Before u Dig”. eservices.dot.gov.in

Frequently asked questions

What colour is used to mark electrical cables?

Red, under the APWA scheme used on most Indian projects. It covers HT and LT power cables, conduits and lighting cables.

What does an orange mark on the road mean?

Communications in most cases: telecom cables, optical fibre ducts, CCTV or signal lines. Check the drawing legend, because in the UK orange ducts are street lighting.

What does a white mark mean?

The proposed excavation, painted by the party who plans to dig, so locators know exactly where to check.

Is the duct colour the same as the mark colour?

Not necessarily, because duct colours vary by owner and supplier in India, so identify the service by survey, not by duct colour.

How long do utility marks last?

Days to a few weeks on asphalt, less in heavy rain or traffic. Coordinates on the drawing let marks be repainted.

Where can I find what QL, offset and no-conflict mean?

See our glossary for details on GPR, SUE & Land Survey Glossary terms used on mark-outs and drawings.

Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026