### ImageMagick version

7.1.1-15

### Operating system

Linux

### Operating system, version and so on

Running portable binary (openSUSE Tumbleweed otherwise)

### Description

A follow-up on #6444. 

I was expecting the 3 channels to be in the conventional order: Lightness, Chroma, Hue. Observed Lightness, Hue and Chroma instead. This can be worked around, but was surprising. 

More importantly, I believe the conversion may not be correct, see example below.

### Steps to Reproduce

Trying to create a rainbow. I picked a lightness and chroma pair where the full hue spectrum can be represented in sRGB.

https://oklch.com/#69,0.113,0,100

```
./magick -size 100x100 \
canvas:'gray(69%)' \
gradient:'gray(0)-gray(255)' \
canvas:'gray(31%)' \
+combine Oklch -colorspace sRGB oklchgradient.jpg
```

produces

![oklchgradient](https://github.com/ImageMagick/ImageMagick/assets/137961841/2e44fc42-52a0-4959-89ba-8002351b0d48)

For comparison, here's one in HSB:

```
./magick -size 100x100 gradient:'gray(0)-gray(255)' canvas:'gray(49%)' canvas:'gray(89%)' +combine hsb -colorspace sRGB hsbrainbow.jpg
```

![hsbrainbow](https://github.com/ImageMagick/ImageMagick/assets/137961841/0a46fa94-5d94-46ee-916b-37ff2da6d234)

Thank you. I know this is a new colorspace and I greatly appreciate any effort that goes into its support.

### Images

_No response_
Oklch channel order, conversion bug
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : Oklch channel order, conversion bug
Issue date:

--- start body ---
### ImageMagick version

7.1.1-15

### Operating system

Linux

### Operating system, version and so on

Running portable binary (openSUSE Tumbleweed otherwise)

### Description

A follow-up on #6444. 

I was expecting the 3 channels to be in the conventional order: Lightness, Chroma, Hue. Observed Lightness, Hue and Chroma instead. This can be worked around, but was surprising. 

More importantly, I believe the conversion may not be correct, see example below.

### Steps to Reproduce

Trying to create a rainbow. I picked a lightness and chroma pair where the full hue spectrum can be represented in sRGB.

https://oklch.com/#69,0.113,0,100

```
./magick -size 100x100 \
canvas:'gray(69%)' \
gradient:'gray(0)-gray(255)' \
canvas:'gray(31%)' \
+combine Oklch -colorspace sRGB oklchgradient.jpg
```

produces

![oklchgradient](https://github.com/ImageMagick/ImageMagick/assets/137961841/2e44fc42-52a0-4959-89ba-8002351b0d48)

For comparison, here's one in HSB:

```
./magick -size 100x100 gradient:'gray(0)-gray(255)' canvas:'gray(49%)' canvas:'gray(89%)' +combine hsb -colorspace sRGB hsbrainbow.jpg
```

![hsbrainbow](https://github.com/ImageMagick/ImageMagick/assets/137961841/0a46fa94-5d94-46ee-916b-37ff2da6d234)

Thank you. I know this is a new colorspace and I greatly appreciate any effort that goes into its support.

### Images

_No response_
--- end body ---

The issue describes a potential bug in the Oklch color space conversion in ImageMagick v7.1.1-15, where the channel order is not as expected (Lightness, Chroma, Hue) and may lead to incorrect color representation. This could result in unexpected behavior when generating images, but it does not indicate a security vulnerability.