Great! Based on your input of black, white, and blue, I’ll create a modern and sleek color palette that includes a background, text, primary action, secondary action, and accent colors, ensuring WCAG 2.1 compliance.

 <Modern Blue Theme>
1. Background - 
          
          #FFFFFF
        - A clean and crisp white that serves as the canvas for the design, offering a bright and spacious feel.
2. Text - 
          
          #000000
        - Deep black for text, ensuring high legibility and contrast against the white background.
3. Primary Action - 
          
          #007BFF
        - A vibrant blue that stands out, perfect for buttons and links to encourage user interaction.
4. Secondary Action - 
          
          #0056b3
        - A darker shade of blue for secondary actions, providing a subtle distinction from the primary action color.
5. Accent - 
          
          #FF5733
        - A striking coral red to draw attention to important elements or notifications, adding a touch of warmth to the palette.

Palette Description:

This color palette embodies a modern and professional aesthetic, utilizing a classic combination of black and white complemented by a vibrant blue for actions. The accent color adds visual interest and can be used sparingly to highlight key elements, ensuring the overall design remains clean and user-friendly.

Follow-Up Questions:

1. What type of application or website are you designing? (e.g., corporate, e-commerce, portfolio)
2. Do you need specific shades or variations for hover states or disabled elements?
3. Would you like to explore additional colors or themes to expand this palette?