Color by axis will highlight lines that are not perfectly on axis as if they are. Be warned.
Yes. They are close.
From February of 2015:
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Yikes, I’ve been instructed by big fish in the SketchUp community to check “square” with this function and have been doing so for many moons.
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It’s pretty good but due to tolerances there are limits. I don’t generally recommend it for critical checking when users share files in which they have difficulties with getting faces to fill. Instead I use coordinates of endpoints to check and show when there are issues.
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Yes. Like that. And in that case, it would be the Y-value that would be primarily of interest. Of course that’s off by less than 3/64 in. end to end or .0022 in. per foot. I’d be willing to bet that’s still a little tighter than the actual building will be built to.
I was commenting about the first image you posted but the point stands.
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Sorry, I changed the image up on you last second, but yea I just realized that its lined up in “XYZ” (not XYV) (green, red, blue) order
x, y, z 
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I think the only time you would see a post from me about color by axis would be to warn that it isn’t accurate.
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Curious.. is this a more metric unit problem than imperial unit because of the original base unit decision of “inches” or is to derived from some other factor?
Long standing and often repeated piece of common knowledge here that Color By Axis has a tolerance and can certainly give false positives at very slight deviations off of axis. Things can present as square when in fact they are not. There are whole threads exploring the exact tolerance that yields false positives, can’t remember what it was off hand. Color by axis is good for a quick check of a model but I think can not be considered a definitive indication of “square”. Only measuring with a fine display unit, or using label tool to give XYZ can be trusted.
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Having Length snapping on will increase the probability of these glitches to happen.
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yes, that was a frustrating lesson to learn. still using 2021 SU here, is the default 2025 install still leaving that on?
So glad this topic came out, I had no clue. Although I constantly use the axis locks when creating lines.
This doesn’t really have anything to do with using the axis locking feature.
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Axis locking via the arrow keys IS guaranteed to be on axis, that’s different than this conversation. The color by axis edge style option is the one discussed here that has a tolerance.
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I’ve read this thread, and I’m left with a question: If you set your Style to Color by axis, when you draw a line that is on the red axis, SketchUp reports exactly the same thing as when you draw a line constrained with the right arrow key. That is, “On Red Axis”. So I’m left with wondering if SketchUp is giving incorrect on-screen reporting?
Edges drawn while locked on axis (using shift or arrow keys) are indeed 100% on axis. Edges incorrectly drawn within a small angular margin off axis will display as their respective color when the edge color by axis style is enabled, misleading the user into thinking they’ve drawn “straight” lines, when in actuality it’s a hair off. But we are talking about a small fraction of a degree off. This isn’t a big deal in 90% of use cases, but it gives me the Sully from monsters inc reaction every time I’ve found out my lines aren’t actually straight, and I didn’t realize that color by axis was not a good tool to check for 100% accuracy.
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Also consider that geometry might become very slightly distorted during other processes such as moving geometry or perhaps during Intersect Faces.
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I’ve re-read this thread carefully, and it makes no sense to me. The geometric state of a line being parallel to an axis is pure math. Since SketchUp calculates to 15 or 16 decimal places of accuracy, there is no logical reason setting the Style to Color by axis should not be perfect. The beauty of a vector graphics program is that it’s dealing with values. It seems there must be some problem within SketchUp that creates an issue, an issue I’ve never had to deal with. I find that Color by axis is a perfectly reliable tool, especially when drawing lines in 3D space. There have been instances where I picked a point on a different plane than intended. Setting the Style to Color by axis shows the error immediately.