This isn't really a Notes/Domino tip, although my applications have certainly benefitted. For those of you (like me) who are color-challenged, coming up with a color scheme for a new app is difficult. How many times can you do shades of gray? But you don't want the yellow, purple, and red nightmare that every company has one of, right? That's where this little site comes in handy. You can enter a starting hex value or choose from a color wheel, and it generates a nice coordinated palette for you. You can then create variations on the palette, like pastel, contrast, etc. There's even a dropdown that lets you view the palette as it appears to various types of color-blindness. It then provides you with the hex values of all the colors in the palette.
Which you can then take over here to convert to Notes-friendly RGB values.