<Modified Rainbow Palette>
1. Red - 
                            
                            #FF4D4D
                         - A softer red that retains vibrancy while providing a more balanced tone.
2. Orange - 
                            
                            #FFB84D
                         - A lighter, less saturated orange that appears warm without leaning towards brown.
3. Yellow - 
                            
                            #FFFF66
                         - A mellow yellow that offers brightness while ensuring readability against black text.
4. Green - 
                            
                            #66CC66
                         - A fresh, softer green that conveys growth and complements the palette harmoniously.
5. Blue - 
                            
                            #6699FF
                         - A calm blue that adds a sense of tranquility, less saturated for better readability.
6. Violet - 
                            
                            #B366FF
                         - A gentle violet that maintains its soothing quality while being easier on the eyes.

This modified color palette presents a softer approach to the rainbow spectrum, ensuring that all colors are less saturated and will work effectively with black text. The adjustment to the last three colors to green, blue, and violet enhances the overall readability and aesthetic.

Do you need any further adjustments or assistance with applying these colors in your Excel document?