One trick you can use if you want temp color without bleaching is to use Pastels, not the oil based ones, the chalk ones. You run them through your hair and after you get the color in use a hot curling iron or what ever hair iron you use. Heat it to set it and it will wash out in a few days. You can find them fairly cheap at Michaels or other art/hobby stores, ($4.99 at Michaels and they have 40% coupons in the paper).
Manic Panic has some good colors but tend to fade quickly. On darker hair depending on the color you are going for you do need to bleach it to get the color you want. All of the samples shown at the store are bleached first.
Otherwise, if you are going for a more permanent look I suggest actually going to a hairdresser that uses Goldwell Illumine products. When I have mine done it doesn't fade for months. There are hairdressers that will work with you on a sliding scale to what you can afford because a: you help promote for them b:they would rather see it done right c: they would rather receive some money than no money at all...
Guessing that manic panic is a brand of hair dye, if you want the color to actually show and actually stay, you will have to bleach it. Sucks, I know. But if you only want it for like a night, you could use hair chalk
Manic Panic has some colors that work great on dark hair with no bleaching. Try Vampire Red, Hot Hot Pink or Purple Haze. You can see examples on their website. The Manic Panic won't make your hair lighter- for that you would have to bleach.