So here's the scoop Vanessa.....
If you have naturally dark hair - Level 1, 2 or 3 with 1 being Raven Black, if you apply purple hair dye to your hair without bleaching it, you will not see the color. That's the simple fact. I don't care what anyone tells you.
Think about it this way. If you had a raven black wall and painted it purple, would the purple show up or fade right into the black?
Hair works under the same principle. Whatever the base color is what will dominate.
If you hair is light or a Level 10, 9, 8 with 10 being platinum or white, applying purple hair without bleach or a lifting agent will give you a light lavender or possible even a lilac. You would need to apply really dark purple to a Level 10, but probably not to a level 7-8 which is light enough to absorb the purple but NOT turn it pink.
Bottom line...you have to start with any hair color change by looking at the current or natural base color. When the base color - natural or currently dye - is dark, you will HAVE to bleach or lift the color for the new color to show up. That's it. Maybe other's have been able to achieve this without bleach, but I have never seen it in the 15+ years I've been in the hair world.
I have a relative with level 5 brunette hair apply Manic Panic DayGlo green to his hair and you couldn't see any of the green. He was upset because he went to all the trouble to apply it. The problem was his hair was too dark for the green to show up.
If you don't want to dye all of your hair, just do some random sections. OR you can go with pre-color clip-ins or fusion hair extensions. Many people, include celebs are doing that. This also eliminates how fast purple hair or similar color fade.
Finally, if you do decide to bleach and go with a MP purple or similar, just use the Manic Panic Flash Lightening Bleach. It works, they've been selling it for years and they will help you if you have problems.
Good luck and if you do it, less us know how it turns out.