Sorry it took me so long to respond..I haven't had time to get to my computer.
I'm not the best at explaining things so just try to bear with me haha. I think a good starting point with the pink it to decide exactly what color you want....pastel pink, hot pink, dark pink, blue based pink, etc. That will determine how light you need your hair to be before applying the dye. The lighter the hair color the closer to white your hair will need to be for it to show up and the faster it will usually fade. Darker colors start out more pigmented then tend to turn pastel-ish as they fade.
Here are pictures of my hair with a few different pinks
First up is Manic Panic cotton candy pink...their lightest color. My hair was the whitest blonde possible for this to show up
As you can see the isn't all that pigmented and you can see spots where it didn't take all the way right next to my ear. This faded out after about 10 days
Next is Manic Panic Hot Hot Pink...this is the one most people use. It's a blue based medium pink and your hair has to be pretty light for it to show. I had streaks of purple and teal MP in my hair as well
This is what it looked like after about 2 weeks then at 3 weeks...very noticeable fading
This is what my hair looks like as soon as I dye it using Jerome Russell Flamingo pink hair color. You can see how the color turns out much more even and pigmented.
This is my hair faded after 6 weeks and 10 weeks
I get about 10 weeks of color out of the Jerome Russel while the Manic Panic fades to the same color after only 3 weeks. I also don't have to lighten my hair as much to use the Jerome Russell since it's a darker, more pigmented dye.
*edit* going to post next about the red dyes...wanted to submit this before i screw it up somehow lol