by steps
000000 000000
000000
0000ff 0000ff
0000ff
00007f 00007f
00007f
007f00 007f00
007f00
007f7f 007f7f
007f7f
1919f8 1919f8
1919f8
007fff 007fff
007fff
00ff00 00ff00
00ff00
00ff7f 00ff7f
00ff7f
3333f2 3333f2
3333f2
00ffff 00ffff
00ffff
7f0000 7f0000
7f0000
7f007f 7f007f
7f007f
4c4cec 4c4cec
4c4cec
7f00ff 7f00ff
7f00ff
7f7f00 7f7f00
7f7f00
7f7f7f 7f7f7f
7f7f7f
6666e6 6666e6
6666e6
7f7fff 7f7fff
7f7fff
7fff00 7fff00
7fff00
7fff7f 7fff7f
7fff7f
7fffff 7fffff
7fffff
7f80df 7f80df
7f80df
ff0000 ff0000
ff0000
ff007f ff007f
ff007f
ff00ff ff00ff
ff00ff
9999d9 9999d9
9999d9
ff7f00 ff7f00
ff7f00
ff7f7f ff7f7f
ff7f7f
ff7fff ff7fff
ff7fff
b2b3d3 b2b3d3
b2b3d3
ffff00 ffff00
ffff00
ffff7f ffff7f
ffff7f
ffffff ffffff
ffffff
cccdcd cccdcd
cccdcd