DMR Colour Codes Explained

In DMR (Digital Mobile Radio), a colour code is like a digital access key for a radio channel.

If the colour code doesn’t match, the radio won’t hear or transmit on that channel.

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What is a Colour Code?

• A number from 0 to 15
• Set on:
  • The repeater
  • All radios that use it
• Must match exactly

Think of it like:

A Wi-Fi password, but numeric and very simple.

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Why colour codes exist

Colour codes:

• Prevent interference from nearby DMR systems
• Stop radios accidentally hearing other organisations
• Replace analogue CTCSS/DCS tones

So:

• Same frequency + different colour code = no interference

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Simple analogy

Analogue	DMR
CTCSS tone	Colour Code
Channel squelch	Digital access key

If your radio is set to CC 3:

• It ignores all traffic using CC 1, 2, 4…15

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How many colour codes?

• 16 total → 0 to 15
• Most systems use CC 1, CC 7, or CC 10 (but any can be used)

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Colour Code vs Talk Group vs Time Slot

These are different things and often confused:

Feature	What it does
Colour Code	Access to the channel
Time Slot (TS1 / TS2)	Splits the frequency in two
Talk Group	Who you talk to

All three must match for communication.

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Example (real-world setup)

Hospital DMR repeater

• Frequency: 450.125 MHz
• Colour Code: 7

Talk Groups:

• TG 101 – Security (TS1)
• TG 102 – Porters (TS2)
• TG 999 – Emergency (TS1)

If a radio is set to:

• CC 7 ✔
• TS 1 ✔
• TG 101 ✔

It hears Security only

Wrong colour code?
Nothing heard at all.

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Can you scan colour codes?

Yes:

• Many DMR radios have promiscuous mode
• Or CC scan to detect the active colour code
• Used by engineers during setup (not day-to-day users)