For others looking for a far simpler and infinitely flexible solution:
Get an APA102C RGB or similarly powerful LED strip, a matching 5V power supply, a 1000uF capacitor and an Adafruit Trinket 5V and wire it up as per the many online instructions available.
Install the FastLED library and get the palette knife browser extension.
And then, you can chain any kind of sky, cloud, submarine, etc. gradient over time with very little code and exact timings, in case these are needed.