What about your light colored girl? Could you not color her instead? I wouldn't risk bleaching unless I was very experience w/ coloring dog and working w/ bleach. Do you know if you boy will hold still during the whole process? Will he try to lick anything? Will you be working in a well ventalated area so the fumes won't get to either one of you? I honestly don't like haveing my own hair bleached (highlighted) and I have it done by a pro. Bleach can also be very damaging. It's also difficult to bleach black hair to the point you need. Most likey it will end up orange.
I am not a dog groomer, I am a hairdresser. I would personally never put bleach on a dog. There are very few bleaches that are safe on the scalp of a human being. Even with those, if you get it on your hands, it starts "eating away" at your skin and burning. And, like Harley Chik says, it so SOOOOO hard to bleach black hair. It could take several applications to get it to be "duckling yellow." It will most likely end up orange. I would not recommend it for a dog. What if your dog paws it, then gets it in his eyes or mouth? Just my opinion....
I have seen it done at grooming competitions. Those dog owners are asked a million questions to verify that nothing unsafe is used on the dog. One person who did a beautiful harelquin clown design was Dawn Omboy, called the queen of color. She might be able to tell you what was safe on her solid black dog to put such vivid colors on her dog. I have seen that stuff at Hot topic that is used to lighten brown hair if you want a few blue or pink streaks. Don't know if it works, though.
I really agree with Skye, I don't think you should bleach your dog's hair. The bleaching process is probably risky with a dog, and I wouldn't trust anyone but a serious pro to do it (like the person P2P mentioned).
I wouldn't risk possible damage to your dog's skin (or if he managed to ingest some of it...) for something as silly as a bit of color (although coloring is really fun, it shouldn't endanger the dog, ever)
If you really want color, you could try that temporary spray-on color at drug stores- it's that really cheap stuff you just spray on the hair, it's vibrant colors and would probably be a lot safer to use on your dog's hair than bleach (so long as you shielded his face with something while you sprayed, don't want that stuff in the eyes/mouth). It washes out (and a lot of it brushes out as well lol) so it's good for events. It works on dark hair- I have dark brown hair and I use it sometimes at school events/for fun, it shows up fine.
Well, all I'm saying is check out some other options instead of bleaching his hair to get color... I find that a bit extreme.
its just something i was thinking of trying so i can have fun making it different colors, but honestly im not feeling good about using bleach on him, im just a bit too worried it will hurt him. But thank you all for your advise.