A bit of information and two LCH color wheels:
XYZ is based on color matching experiments and reflects the linear behavior of light.
LAB is intended to be a perceptually uniform mathematical transform of XYZ, such that equal distances between pairs of LAB coordinates cohere with our perception of “equally far apart colors”.
LCH is a straight-foward polar transform of LAB. This means that an LCH color wheel is also a LAB color wheel. Given the a and b coordinates of any LAB color located on the LAB/LCH color wheel:
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LCH “Chroma” is the square root of the sum of the squares of a and b (this is just the mathematical formula for calculating the distance of a point on a 2D cartesian graph to the intersection of the two axes).
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LCH “Hue” is the angle between the positive “a” axis (Hue=0/360) and a line drawn from the color’s (a,b) coordinates to the intersection of the a and b axes (where a=b=0).
The third axis of both the LAB and LCH color spaces is “L” for “Lightness”. The “Lightness” axis is perpendicular to the ab/Hue-Chroma plane. So you would need a 3D “LCH color sphere” to show all three axes at once.
The handprint.com website has a nice downloadable LAB color wheel that shows the LCH Hue angles and Chroma values for commonly used watercolor pigments. Directly posting images from the handprint.com website would violate the handprint.com copyright, but here’s the link if you want to download the color wheel for personal use: handprint : CIELAB ab plane.
Here is a blank LCH color wheel licensed as CC-BY-SA in case anyone wants to try their hand at using the new GIMP LCH color readouts to locate sRGB colors on an LCH color wheel:
It’s interesting to see where the sRGB red, green, and blue primaries fall on the LCH color wheel. For example sRGB bluest blue (0.0f, 0.0f, 1.0f) has an HSV Hue of 240, but an LCH Hue of 301, which is decidedly on the magenta side of LCH violet-blue.
Actual sky-blue colors - measured as wavelengths and converted to LAB/LCH - are centered at roughly LCH Hue 250-255, but vary quite a bit between LCH cyan-blue and LCH violet-blue, depending on a host of factors that affect the color of a blue sky. So a naive interpretation of HSV Hue 240, might lead one to assume that sRGB’s bluest blue really is “blue sky blue”, but this would be incorrect.
@afre - you’ve mentioned difficulties with dealing with colors. I have the same problem when painting and when modifying colors in photographs, which is a major reason why I started making use of LCH color information. I figure that if my blue sky is in the range of believable sky blue colors, and my green leaves are within the range of normal healthy green plant colors, and so on, that’s a good thing!