When considering bleaching your hair before dyeing, there are a few factors to consider:

1. Current Hair Color: If your natural hair color is darker than the shade you wish to achieve, you may need to bleach your hair to remove the existing pigment so that the new color will show up correctly.
2. Desired Hair Color: For very light shades or vibrant colors (like pastels, bright reds, pinks, or purples), bleaching is often necessary to achieve the light base needed for the color to appear true to tone.
3. Hair Type and Health: The condition of your hair is crucial. If your hair is already damaged, bleaching could further damage it. It's important to assess the health of your hair and perhaps do a strand test first.
4. Professional Help: Bleaching can be harsh on the hair and requires careful application to avoid uneven results or damage. If you're unsure about how to bleach your hair safely, it's recommended to seek professional assistance at a salon.
5. Timing: Typically, you would bleach your hair immediately before coloring it. This ensures that the hair cuticles are still open from the bleaching process, allowing the dye to penetrate effectively. However, if your hair feels very dry or damaged after bleaching, it might be beneficial to wait a day or two to give your hair a chance to recover slightly with the help of deep conditioning treatments.
6. Aftercare: After bleaching and dyeing, it’s important to follow up with intensive conditioning treatments to help repair the hair and maintain its health.

Remember, bleaching and coloring can be stressful on your hair, so proper preparation and aftercare are key to achieving the desired results without compromising the health of your hair.