Based on the colors you’ve mentioned, I’ve created a complementary color palette that harmonizes with the existing colors of Vallejo Game Color Steel Grey, Vallejo Model Color Red, AK Interactive Medium Rust, and Vallejo Game Color Jade Green. This palette focuses on balancing earthy tones with vibrant accents.

 < Earthy Vibrance > 
1. Slate Blue - 
                            
                            #6A7B9D
                         - A muted blue that adds depth and coolness, complementing the warmth of the rust and red.
2. Goldenrod - 
                            
                            #DAA520
                         - A warm yellow that enhances the earthy tones and provides a bright contrast.
3. Charcoal - 
                            
                            #36454F
                         - A darker grey that can ground the palette and provide a strong neutral backdrop.
4. Coral - 
                            
                            #FF6F61
                         - A soft, warm coral that harmonizes beautifully with the red while adding a touch of vibrancy.
5. Olive Green - 
                            
                            #3A3D2A
                         - A muted green that ties in with the jade green, creating a cohesive look with an earthy feel.

This palette creates a balance between vibrant colors and muted tones, suitable for a wide range of design applications, especially in gaming or artistic contexts.

Would you like to explore more colors or perhaps a specific theme for your project?