I absolutely love YouTube and the wonderful (generous) artists who create tutorials and upload them there. One I found a while back and rediscovered it recently features a calligraphy pen called the Elegant Writer by Speedball. Someone figured out that the black ink in that pen, when activated by water, bleeds out in shades of gray, blue, purple, pink and even some greens. These colors are spontaneous, you can't really control the colors, but if you blot the ink/water mix while it's still wet, you can bring out the more pinky colors.
I am experimenting with this pen now, since I love watercolor, this is a natural for me, you can leave the colors that happen as is, or you can add more color with watercolor, colored pencil or whatever you like, you can also add Micron pens to the mix, those do not bleed when wetted with water.
Here is a quick card I made just a few minutes ago, with the exception of the green in the stem, all the rest of the color happened as a result of using the Elegant Writer and water. I wrote the quote using the Elegant Writer but chose not to wet that, preferring the crisp letters.
Let me know what you think?