Fractal Extreme has two 228 colour palettes. The 2nd palette is only shown if the 'show stripes' option is used, every even index from the 1st every odd from the 2nd, so still just 228 possible colour indexes. If antialiasing is enabled Fractal Extreme will interpolate a colour between these palette indexes assuming colour mapping speed or acceleration are greater than 1 (ie spreading a colour across multiple iteration bands). In this palette I've used all 228, roughly covering the colour cube then sorted the various colours into a blue, cyan, green, white, magenta, red, yellow and black sequence. This is all done in a spreadsheet, which allows me to simply offset the stripe palette by 16 places. If you do the math 228/8 gives 28.5 palette index per colour so a 16 offset blends the colours nicely. The sorting is done on high bit so any colour with all three RGB values less than 128 I call black, Red greater than 127 but green and blue less than 128 I call red and so on. I then sort by the next highest bit so a Red value less than 192 is sorted within the 28 or so red values as black, theres a different sort sequence for each main seqence colour so that BLUEcyan get sorted next to CYANblue. Theres still 2 or three colours within this 'next highest bit' sequence so the 3rd most significant bit get sorted in a similar fashion.
Please don't get the idea that Fractal Extreme has some sort of import from spreadsheet option, this is a program that I wrote after analyzing the fractal extreme palette file with a hex editor.
Fractal Extreme has a very good palette editor, and I've just figured out how you can do similar without having to resort to spreadsheets.
First take a palette
Then offset by 16 places by clicking the slider then hitting cursor left 16 times.
Now right click and select all from each of the Red Green and Blue Windows, you'll need to hold shift for the 2nd & 2rd select all. Edit-> copy and you now have the offset pallette in the paste buffer.
Load a 2nd palette or in this case the same palette to remove the offset.
Make sure Colour-> show stripes is enabled and Colour->edit odd.
Edit->paste and now you've duplicated and offset the palette.
A few further things about Fractal Extreme's palette editor, it is completely resizable, I just used the minimum size for these attachments. You can bound box a series of palette index points or shift select a group of individual points. Then you can drag all the selected points as one, say reducing the level to create as subtle or brutal stripe as you like or offsetting ( a more sparse palette than my completely filled ones) to create colour striping effects.