It seems to be a bug. I tried a moment ago to change my RGBW Smart Bulb to turquoise by Alexa command and it does works? Did you tried with a Voice Assistant instead of the app? Maybe it’s a bug related to app.
I am having the same issue. If I select Turquoise on the colour picker (as illustrated above). I get an orange/yellow hue.
I’ve had lots of issues with the lightstrip lately, and flowing through turquoise to a different colour does not work, it skips turquoise and goes orange/yellow instead.
Till now also no Turquoise colour. Just bought 3 Yeelight strip plus in July and upgraded the firmware, still no Turquoise colour. Really disappointed! wanted to sell away if nothing done. No point having nice selection and can’t accurately select the colours. Try Google assistance also no use. Google home also cannot control the preset colours. What’s goes wrong.
I have the same problem but i noticed that the lights can do those colors because if u set in a certain way the color flow, when it changes the color it make blue sky, turquoise, light blu ecc. It’s a software problem i hope they’re gonna correct this ERROR very soon cause with RGB the colors you can make are always those even on cheap or expensive lights.
I tried the flow option and it still turns white I hope they can fix it because turquoise/ cyan is my favorite colors and I was planning on using these for my table.