Sure! Here’s the updated color palette with a darker shade of blue:

 <Cold Hearted Character>
1. Midnight Black - 
                            
                            #000000
                         - A deep, intense black that embodies darkness and mystery.
2. Icy White - 
                            
                            #F0F0F0
                         - A stark, crisp white that represents coldness and detachment.
3. Deep Frost Blue - 
                            
                            #0D4F8B
                         - A darker, richer blue that conveys a sense of chill and aloofness.
4. Steel Gray - 
                            
                            #A9A9A9
                         - A muted gray that reflects a hardened, emotionless attitude.

This adjusted palette maintains the cold and isolating theme while enhancing the depth of the blue shade, thus reinforcing the character’s cold-hearted nature.

Would you like any further adjustments or assistance with how to use this palette in specific designs?