Based on the colors you’ve provided (Vallejo Game Color Steel Grey, Vallejo Model Color Red, Vallejo Game Color Jade Green, AK Interactive Medium Rust), here’s a complementary color palette that can enhance your existing colors:

 <Complementary Palette>
1. Charcoal Black - 
          
          #333333
        - A deep, dark black that adds depth and contrast to your palette.
2. Warm Beige - 
          
          #D6CFCF
        - A soft, warm beige that complements the rust and provides a neutral backdrop.
3. Bright Amber - 
          
          #FFC107
        - A vibrant amber hue that contrasts nicely with jade green and adds warmth.
4. Cool Mint - 
          
          #A4D7E1
        - A soothing mint green that balances the intensity of the red and rust.
5. Deep Plum - 
          
          #6F2C91
        - A rich plum that provides a striking contrast while harmonizing with the red tones.

Description:

This complementary palette features a mix of deep, neutral tones and vibrant accents. The Charcoal Black provides a strong foundation, while Warm Beige softens the overall look. Bright Amber introduces warmth and energy, Cool Mint offers a refreshing touch, and Deep Plum adds a rich contrast, making it a versatile set for various design applications.

What type of project are you planning to use this palette for? Are there specific emotions or themes you want to focus on in your design?