the "Safe" colors, shown below, appear the same on all monitors and web browsers...
to view all the colors, click here

Red and Green (#rrgg00)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red and Blue (#rr00bb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Green and Blue (#00ggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

gray (#rrggbb)

000000 333333 666666 999999 CCCCCC FFFFFF

Red = 33 (#33ggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red = 66 (#66ggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red = 99 (#99ggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red = CC (#CCggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red = DD (#DDggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF

Red = FF (#FFggbb)

0000 3300 6600 9900 CC00 FF00
0033 3333 6633 9933 CC33 FF33
0066 3366 6666 9966 CC66 FF66
0099 3399 6699 9999 CC99 FF99
00CC 33CC 66CC 99CC CCCC FFCC
00FF 33FF 66FF 99FF CCFF FFFF