It seems like an evidence but shoot in raw format in this case because:
color temperature change and jpeg need to preset the temperature reference so once shoot and write in the file, the original information is lost, translate to the new reference. It is hard to rechange to another reference without loosing more info. Raw files are the information directly output by the sensor, with few interpretation (protocol, file format/info are added info, ...) and color temperature is just an info telling how to deal with the content but this can be changed at creation of the jpg (or other format) via the tools you use to extract picture.
Raw format allow (and use) a bigger scale to store elementary color information (more bit) that allow to have more subtility that are very interresting at the edge of the scale. The information is not available in jpeg (a average value making big step in perception in lower light that eye could easily see). Post processing is needed to use this information in raw but with the possibility to rescale with your own average taht will better suite, from your perception pint of view, to the picture.
Why is it nearly mandatory in sunset:
For the hight ISO, the modification of ISO is in fact an amplification of the signal of the cell from the sensor, not like the old roll film that change the nature of the sensor itself. This means that noise (electronic concept) is also amplyfied and other specific problem appear (especialy for long exposure). This will modify color and light perceived by the sensor (the output of the sensor, sensor is not changing the light ray). This will create a difference with real color/light and the write info into the file.
High ISO are interessting to still take a picture when light is low but the cost is the noise in color and intensity. The noise is a bit hazardous and 2 shoot in same condition will give you 2 different picture where low ISO (low mean the nearest value to the real sensitivity of the sensor, not the lowest available on the camera) will give (with enough light) 2 nearly identique picture.
You also need to know that, as you know, lower ISO will also say longer exposure at same aparture, have another side effect on sensor. The longer the sensor is "open", the more heat is generated and heat have a similar effect on the output than amplification, it create noise.
So, you need to find the optimum between ISO and exposure time to reduce the perturbation.
Last important point is the way modern sensor perceive the color. Appart some special sensor like the foveon of sigma, all sensor can only see light intensity, not color light intensity nor color itself. A specific matric of colored micro lens at put in front off sensor (bayer matrix) and color is interpreted for this information. (schema of a bayer matrix)
Because each elemetary color is not see the same way depending intensity, the interpreted value is giving the bad info (ex: if on 2 cell sensor see 1 red at 75% and 1 green at 75% that give a green olive, reducing the light could give a red at 30% and a green at 15% giving dark brown and not a dark green olive)