Why does Level 424 need a white buffer?

The four 40-stacks and the yellow key release share the same limited holes; one empty lane is required for the next color to surface.

What is the last recognizable part of the target?

The full spiral collapses to a small central curl with a few orange, cyan, green and purple pixels; wait until that curl is also gone.

Colony Flow! level guide

hard 10 colors

Peel a rainbow spiral through orange 3/16 and staggered 40-stacks while keeping a buffer for the yellow key release.

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Tap orange/yellow 3 and orange/yellow 16, then wait for the short yellow ants to return before using the first purple lane.
Route the exposed purple stack and pink/red 35 while keeping the yellow key slot and one white buffer lane available.
Feed purple 40, green 40 and the second purple 40 one at a time; let each long perimeter stream clear before taking red 40.
Use green 36, blue 30 and blue 30 to open the upper cyan/blue band, then route green 38 after the right edge is free.
Continue with purple 32/29/26/23/21/19/16 and cyan 34/30/29/26 as the outer spiral bands separate; wait whenever the lower edge is crowded.
Use orange 50/47/42/34 and pink/red 35/34/32/24 to remove the left and lower bands, preserving a hole for the yellow key release.
Clear the short green 7/3/2 and purple 12/8/6/5/3 cards around the remaining blue crest and central curl.
Finish the tiny orange, green, cyan and purple spiral pixels, then wait for every ant to leave and confirm the board-clear animation.

Colors in this level:

Orange, Yellow, Purple, Pink, Red, Green, Cyan, Blue, Dark blue, White

Starting all four visible 40-stacks before the yellow key opens fills the buffer and stalls the spiral's next release.
Tapping a new orange or purple stack while the lower perimeter is crowded hides the safe blue/green return lane.

Use orange/yellow 3 and 16 before committing to the four long 40-stacks.
Stagger purple 40, green 40, purple 40 and red 40; never fill every route while the key is closed.
Wait at the lower edge so late blue and green stacks can return instead of hiding behind the spiral.

Board notes 5 details

Layout: A complete rainbow spiral or shell made from orange, yellow, green, cyan, blue, dark-blue, purple and pink bands. The opening row shows orange/yellow 3, orange/yellow 16, a partly covered purple stack, pink/red 35 and an empty slot. The next rows show purple 40, green 40, purple 40, red 40, green 36, purple 40, blue 30/30 and green 38, with a yellow key lock at lower left.
Goal: Peel the outer rainbow bands through matching holes, open the yellow key lane, reduce the board to the central curl and remove the final orange, green, cyan, blue, purple and pink pixels until the board is empty.
Opening: Tap orange/yellow 3 and orange/yellow 16 first, then use the returned space for the exposed purple and pink/red stacks. Wait for the short yellow ants before starting the long 40-cards.
Danger Zone: Purple 40, green 40, purple 40 and red 40 can fill all five slots before the yellow key opens. Keep one white buffer slot free and wait when purple or orange ants cover the lower edge.
Mechanics: A long hard-level perimeter-traffic board with a limited buffer, a yellow key release and a rainbow-spiral pixel-art peel from complete image to central curl.

Why does Level 424 need a white buffer?
The four 40-stacks and the yellow key release share the same limited holes; one empty lane is required for the next color to surface.
What is the last recognizable part of the target?
The full spiral collapses to a small central curl with a few orange, cyan, green and purple pixels; wait until that curl is also gone.