Thank you for your patience! Let’s incorporate a yellow/gold tone for the CTA to align with your vision. Here’s the updated color palette:

 <Modern Cold Greyscale with Gold CTA>
1. Primary Blue - 
                            
                            #0077CC
                         - A vibrant blue that serves as the primary color, conveying trust and professionalism.
2. Golden Yellow - 
                            
                            #FFC107
                         - A warm gold that is striking yet inviting, perfect for call-to-action elements.
3. Light Grey - 
                            
                            #D9D9D9
                         - A soft light grey that provides a neutral background, ensuring other colors pop.
4. Medium Grey - 
                            
                            #A6A6A6
                         - A mid-tone grey for text and secondary elements, offering a contemporary feel.
5. Dark Grey - 
                            
                            #4D4D4D
                         - A deep grey that can be used for headers and footers, enhancing readability and contrast.

The golden yellow will add a touch of warmth and positivity while still being visually appealing alongside the primary blue and greys.

Does this palette meet your expectations, or would you like to explore further options or adjustments?