I want to make Halloween cookies but am unsure about coloring RI black. Is it like regular icing where you need to just add alot of color? Is there a hidden trick? Can too much color ruin the RI?
Also, can you put other colors on top of it? i.e., eyes on a black cat.
I haven't made many cookies so be gentle! 
Thanks
If you use americolor you add alot but not as much as wilton. Start with any dark color, not white, then add enough black to get black. I usually take all my leftover colors of icing and mix them together, then add black. You can also add cocoa powder to darken it if you want your black to taste like chocolate. Yes you can put other colors on top, just make sure the black is good and dry first.
No matter what brand you use, I have found that letting the color "rest" before applying to the cookies helps the color deepen a little.
Good luck!
Another question about black - I've seen some really cool spiderweb cookies where folks have used a white (or other colored) base with black lines; it looks like they were done at then same time and then a toothpick was dragged through for the web look. How can that be done without the black bleeding into the white?? What is the secret? Thanks!
Two things 
:
To get a deep black, I add Hershey's Special Dark to my RI (a trick SweetDreamsAT told me) and then I add my Americolor Super Black. Don't go as deep as you think you might need to as you need to let it sit overnight and then the color will deepen. This way you do not use as much black as you might otherwise.
For the second, the trick to not having your black bleed into your white it is have them both the same consistency and overall with both, have them not too runny. Also, using the technique explained above to get a deep black helps greatly.
Hope this helps!
just to expand on what Tracy said.
the trick to not having the colors bleed (black, blue, green, red, whatever)
is letting the color sit, preferably overnight (and not using too much color).
if you use it fresh it will bleed - not right away - like the next day or something - just to annoy the stink out of you! 
(then again, if you use really 'old' icing you are more likely to get the dreaded popped holes...)
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