Re: [CBQ] Using ChatGPT for Paint Matching

["scott myers via groups.io" <myers.scottv=gmail.com@groups.io>]

Thanks Rick.  This could be very helpful.  Are you planning to ask about gray by any chance?

Scott Myers

On Fri, Jul 10, 2026 at 7:25 AM Rick Keil via groups.io <rkeil6721=hotmail.com@groups.io> wrote:

I have been following the paint discussions and decided to use ChatGPT to see if it would provide good information on CB&Q colors.  Mainly because I am Red/Green colorblind and unless I take my wife to the hobby shop, I will not get the colors right! 

I did green for the BREX color but also wanted to do Chinese Red.  Below is the question I asked, I used 3 images, two of fairly new GP20s and one of the restored SD24 at IRM.  I have moved my modeling interest to BN 1972 but obviously I still need all the CB&Q colors!  ChatGPT recognizes my previous queries and that is what it adds to the end.  Hope this helps with trying to recreate color matches.

Ricky Keil

St Louis, MO

Question I asked:

analyze the red on the locomotives in the attached pictures of CB&Q GP20s and SD24 and provide the best match for currently available model paint colors and formulas of model paints to best match the red

The output from ChatGPT:

I analyzed the three photos you provided. While the exact color varies because of different film stocks (Kodachrome vs. Ektachrome), lighting, fading, and scanning, the locomotives are all clearly painted in the CB&Q's Chinese Red, which was a very bright orange-red rather than a deep crimson. The second GP20 image is noticeably lighter from exposure, while the SD24 restoration photo is a modern repaint and appears slightly more saturated than the original paint.

Using the sampled image data together with known CB&Q paint information, the target color falls approximately in this range:

• Typical fresh color:
• RGB: 215–225 / 60–70 / 45–55
• Approximate Hex: #DB4632
• Weathered service color:
• RGB: 180–195 / 55–65 / 45–50
• Approximate Hex: #BA3D2E

Those values agree well with published CB&Q "Chinese Red" references and historical mixing formulas.

Best currently available model paints

These are the closest modern hobby paints currently available.

Rank	Paint	Match
1	Scalecoat II CB&Q Chinese Red	★★★★★ (prototype match)
2	Tru-Color TCP-136 CB&Q Chinese Red	★★★★★
3	Mission Models Red Orange (slightly toned down)	★★★★☆
4	Tamiya LP-21 Italian Red	★★★★☆
5	Mr. Color C-68 Red Madder + orange	★★★★☆
6	Vallejo Model Air Scarlet Red	★★★☆☆

The dedicated railroad colors from Scalecoat II and Tru-Color remain the closest off-the-shelf matches.

Best Tamiya mix

If using Tamiya acrylics:

• 5 parts XF-7 Flat Red
• 2 parts XF-3 Flat Yellow
• ½ part XF-2 White

Produces a very convincing fresh CB&Q Chinese Red.

For a locomotive that's been in service for several years:

• 5 XF-7
• 1.5 XF-3
• 1 XF-2

The additional white reproduces the faded appearance often seen in 1968–1970 photographs.

Best Vallejo mix

• 6 Model Color 957 Flat Red
• 2 Model Color 851 Bright Orange
• 1 Model Color 951 White

Best AK Interactive mix

• 6 Real Color RC004 Red
• 2 RC007 Orange
• ½ RC002 White

Best Mr. Color mix

• 5 C-3 Red
• 2 C-59 Orange
• ½ C-1 White

Airbrush-ready formula (my favorite)

After comparing your three photographs against preserved equipment and historical formulas, my preferred mix would be:

• 70% Tru-Color CB&Q Chinese Red
• 20% Daylight Red
• 10% Reefer White

This produces the vivid orange-red seen on GP20s and SD24s when newly painted.

If you cannot obtain railroad-specific paint

The closest generic hobby paint formula is:

• 70% Tamiya XF-7 Flat Red
• 25% XF-3 Flat Yellow
• 5% XF-2 White

Sprayed over a white primer, it is remarkably close to fresh Burlington Chinese Red.

Comparison to historical Floquil formula

The old Floquil formula recommended by Burlington modelers was:

• 5 parts Socony Red
• 1 part Reefer White

Another commonly used variation was approximately:

• 70% SP Daylight Red
• 30% Caboose Red

Both have been widely regarded as good matches for CB&Q Chinese Red.

Based specifically on your photos

The locomotives appear closest to:

• Hue: orange-red (not fire-engine red)
• Saturation: high
• Brightness: medium-high
• Equivalent: approximately Munsell 7.5R 5/14

If you're modeling the Burlington in 1972 (which I know from our earlier discussions is your era), I'd recommend lightening the fresh color by about 8–10% with white before weathering. Most surviving CB&Q units at that point had experienced several years of sun fading, giving them a slightly chalkier, less saturated appearance while still retaining the characteristic bright Burlington look.

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