The strandtest is that sketch from the Adafruit Neopixel library ?
The SK6812 is a 4 color led : RGB + White, so maybe there is a specific argument in the constructor
// Parameter 1 = number of pixels in strip
// Parameter 2 = Arduino pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
// NEO_KHZ800 800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
// NEO_KHZ400 400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
// NEO_GRB Pixels are wired for GRB bitstream (most NeoPixel products)
// NEO_RGB Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
// NEO_RGBW Pixels are wired for RGBW bitstream (NeoPixel RGBW products)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(60, PIN, NEO_GRB + NEO_KHZ800);
I’m not fluent in english, so you should read this, maybe you’ll understand better than me. These lines from the .h file explain the parameters of the constructor :
// The order of primary colors in the NeoPixel data stream can vary
// among device types, manufacturers and even different revisions of
// the same item. The third parameter to the Adafruit_NeoPixel
// constructor encodes the per-pixel byte offsets of the red, green
// and blue primaries (plus white, if present) in the data stream --
// the following #defines provide an easier-to-use named version for
// each permutation. e.g. NEO_GRB indicates a NeoPixel-compatible
// device expecting three bytes per pixel, with the first byte
// containing the green value, second containing red and third
// containing blue. The in-memory representation of a chain of
// NeoPixels is the same as the data-stream order; no re-ordering of
// bytes is required when issuing data to the chain.
// Bits 5,4 of this value are the offset (0-3) from the first byte of
// a pixel to the location of the red color byte. Bits 3,2 are the
// green offset and 1,0 are the blue offset. If it is an RGBW-type
// device (supporting a white primary in addition to R,G,B), bits 7,6
// are the offset to the white byte...otherwise, bits 7,6 are set to
// the same value as 5,4 (red) to indicate an RGB (not RGBW) device.
// i.e. binary representation:
// 0bWWRRGGBB for RGBW devices
// 0bRRRRGGBB for RGB
// RGBW NeoPixel permutations; all 4 offsets are distinct
// Offset: W R G B // HEX representation
#define NEO_WRGB ((0 << 6) | (1 << 4) | (2 << 2) | (3)) // 0x1B
#define NEO_WRBG ((0 << 6) | (1 << 4) | (3 << 2) | (2)) // 0x1E
#define NEO_WGRB ((0 << 6) | (2 << 4) | (1 << 2) | (3)) // 0x27
#define NEO_WGBR ((0 << 6) | (3 << 4) | (1 << 2) | (2)) // 0x36
#define NEO_WBRG ((0 << 6) | (2 << 4) | (3 << 2) | (1)) // 0x2D
#define NEO_WBGR ((0 << 6) | (3 << 4) | (2 << 2) | (1)) // 0x39
#define NEO_RWGB ((1 << 6) | (0 << 4) | (2 << 2) | (3)) // 0x4B
#define NEO_RWBG ((1 << 6) | (0 << 4) | (3 << 2) | (2)) // 0x4E
#define NEO_RGWB ((2 << 6) | (0 << 4) | (1 << 2) | (3)) // 0x87
#define NEO_RGBW ((3 << 6) | (0 << 4) | (1 << 2) | (2)) // 0xC6
#define NEO_RBWG ((2 << 6) | (0 << 4) | (3 << 2) | (1)) // 0x8D
#define NEO_RBGW ((3 << 6) | (0 << 4) | (2 << 2) | (1)) // 0xC9
#define NEO_GWRB ((1 << 6) | (2 << 4) | (0 << 2) | (3)) // 0x63
#define NEO_GWBR ((1 << 6) | (3 << 4) | (0 << 2) | (2)) // 0x72
#define NEO_GRWB ((2 << 6) | (1 << 4) | (0 << 2) | (3)) // 0x93
#define NEO_GRBW ((3 << 6) | (1 << 4) | (0 << 2) | (2)) // 0xD2
#define NEO_GBWR ((2 << 6) | (3 << 4) | (0 << 2) | (1)) // 0xB1
#define NEO_GBRW ((3 << 6) | (2 << 4) | (0 << 2) | (1)) // 0xE1
#define NEO_BWRG ((1 << 6) | (2 << 4) | (3 << 2) | (0)) // 0x6C
#define NEO_BWGR ((1 << 6) | (3 << 4) | (2 << 2) | (0)) // 0x78
#define NEO_BRWG ((2 << 6) | (1 << 4) | (3 << 2) | (0)) // 0x9C
#define NEO_BRGW ((3 << 6) | (1 << 4) | (2 << 2) | (0)) // 0xD8
#define NEO_BGWR ((2 << 6) | (3 << 4) | (1 << 2) | (0)) // 0xB4
#define NEO_BGRW ((3 << 6) | (2 << 4) | (1 << 2) | (0)) // 0xE4
Also there is a paragraph about the trinket:
// Add NEO_KHZ400 to the color order value to indicate a 400 KHz
// device. All but the earliest v1 NeoPixels expect an 800 KHz data
// stream, this is the default if unspecified. Because flash space
// is very limited on ATtiny devices (e.g. Trinket, Gemma), v1
// NeoPixels aren't handled by default on those chips, though it can
// be enabled by removing the ifndef/endif below -- but code will be
// bigger. Conversely, can disable the NEO_KHZ400 line on other MCUs
// to remove v1 support and save a little space.
#define NEO_KHZ800 0x0000 // 800 KHz datastream
#ifndef __AVR_ATtiny85__
#define NEO_KHZ400 0x0100 // 400 KHz datastream
#endif
// If 400 KHz support is enabled, the third parameter to the constructor
// requires a 16-bit value (in order to select 400 vs 800 KHz speed).
// If only 800 KHz is enabled (as is default on ATtiny), an 8-bit value
// is sufficient to encode pixel color order, saving some space.