How to Understand Color Theory

RGB, HEX, HSL explained simply. Learn color harmony, complementary colors, and practical design applications.

Color Models Explained

  • RGB (Red, Green, Blue): Additive model for screens. Values 0-255 per channel. rgb(37, 99, 235) is blue.
  • HEX: Hexadecimal RGB. #2563eb = rgb(37, 99, 235). Six hex digits (0-9, A-F).
  • HSL (Hue, Saturation, Lightness): Intuitive model. Hue is 0-360 degrees. Saturation and Lightness are 0-100%.

Converting Between Formats

HEX to RGB:

#2563eb
R = 0x25 = 37
G = 0x63 = 99
B = 0xeb = 235
Result: rgb(37, 99, 235)

Use our Color Picker to convert instantly.

Color Harmony: Creating Pleasing Combinations

  • Complementary: Opposite colors (180 apart). High contrast: blue + orange.
  • Analogous: Adjacent colors (30 apart). Harmonious: blue + teal + green.
  • Triadic: Three colors evenly spaced (120 apart). Vibrant: red + yellow + blue.
  • Monochromatic: Same hue, different lightness. Clean and professional.

Practical Design Applications

  • Backgrounds: HSL lightness 95-98% for light mode, 8-15% for dark mode
  • Text contrast: Minimum 4.5:1 ratio for body text (WCAG AA)
  • Brand colors: 1 primary + 1 accent. SimpyTool uses #2563eb + #10b981
  • Gradients: Analogous colors create smooth gradients

Use our Color Palette and Gradient Generator tools.

Color Psychology and Accessibility

  • Red: Urgency, passion, errors. Use sparingly.
  • Blue: Trust, stability. Most popular brand color.
  • Green: Growth, success. Good for success states.
  • Yellow: Warning. Hard to read on white.
  • Accessibility: Always test contrast. 8% of men have color blindness.

Practical Tips for Working with Color

When building a color system for any project, start with a primary brand color and build outward. A common approach is the 60-30-10 rule: use one dominant color for 60% of the design, a secondary color for 30%, and an accent color for the remaining 10%. This creates visual balance and prevents color overwhelm. Always test your color choices in both light and dark mode, as colors that look vibrant on a white background may become muddy or invisible on dark backgrounds.

Accessibility should be a consideration from the start, not an afterthought. Use a contrast checker to verify that text remains readable against background colors. Remember that approximately 8% of men have some form of color vision deficiency, most commonly red-green color blindness. Avoid relying solely on color to convey information — use text labels, icons, or patterns as redundant cues. Tools that simulate color blindness can help you evaluate whether your design is accessible to all users.

Frequently Asked Questions

What is the difference between RGB and HEX?
They represent the same color model. HEX is RGB in hexadecimal. #ff0000 = rgb(255, 0, 0) = pure red.
What HSL hue value makes blue?
Hue 210-240 gives blue. Pure blue is 240. The full wheel: 0=red, 60=yellow, 120=green, 180=cyan, 240=blue, 300=magenta.
How many colors can RGB represent?
RGB with 8 bits per channel represents 16,777,216 colors. This covers the entire visible gamut for most displays.
What is WCAG color contrast?
WCAG requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text for accessibility.
How do I create a color palette for my brand?
Start with one primary color. Add a lighter variant for backgrounds, a darker variant for hovers, one accent color, and neutral grays.
How do I pick colors that go well together?
Use color harmony rules: complementary (opposite on the color wheel) for high contrast, analogous (adjacent) for harmony, or triadic (evenly spaced) for vibrancy. Start with a base color and generate a palette using these relationships rather than choosing colors randomly.
Should I use HEX, RGB, or HSL?
Each format has its use. HEX is compact and standard for web CSS. RGB is useful for programming and specifying exact values. HSL is most intuitive for humans when adjusting colors, since you can independently control hue, saturation, and lightness. Use whichever is most practical for your workflow.
How many colors should my brand use?
Most professional brands use 3 to 5 core colors: one primary, one or two secondary, an accent, and neutral grays for backgrounds and text. Too many colors create visual noise and dilute brand recognition. Less is almost always more in brand color design.