Here’s an updated color palette with a complementary seventh color that ensures readability with black text:

 <Complementary Palette with Readability> 
1. Golden Yellow - 
          
          #EBC750
        - A vibrant, warm yellow that adds brightness and energy.
2. Lavender Purple - 
          
          #BF74D0
        - A soft, soothing purple that adds a touch of elegance.
3. Sky Blue - 
          
          #7599C4
        - A calm, serene blue reminiscent of clear skies.
4. Rose Pink - 
          
          #C581AB
        - A gentle, romantic pink that brings warmth to the palette.
5. Lime Green - 
          
          #9FC458
        - A fresh, lively green that symbolizes renewal and growth.
6. Terracotta Orange - 
          
          #DE7740
        - A warm, earthy orange that adds a grounding effect.
7. Cool Gray - 
          
          #A3A3A3
        - A neutral gray that provides excellent contrast and ensures readability with black text.

This updated palette maintains vibrant colors while introducing a cool gray that is complementary and ensures legibility when paired with black text. The gray serves as a versatile backdrop that enhances the overall readability of any design.

What specific application do you have in mind for these colors? Would you like help with design layout or typography as well?