color-tools

name	color-tools
description	Work with colors: convert between HEX/RGB/HSL, build palettes, find complementary/analogous colors, and check text contrast for accessibility (WCAG). Use when users ask to convert a color, lighten/darken it, build a color scheme, or check if a color combo is readable. Triggers on mentions of color, colour, hex, rgb, hsl, palette, contrast, complementary, shade, 颜色, 配色, 色值, 对比度, 调色板.
license	Proprietary. LICENSE.txt has complete terms
compatibility	Requires python3. Works on macOS, Linux, and Windows.

Color Tools

Compute color math; don't eyeball hex values.

HEX ↔ RGB ↔ HSL

python3 - <<'PY'
import colorsys
def hex_to_rgb(h): h=h.lstrip('#'); return tuple(int(h[i:i+2],16) for i in (0,2,4))
def rgb_to_hex(r,g,b): return '#%02x%02x%02x'%(r,g,b)
r,g,b = hex_to_rgb('#3b82f6')
h,l,s = colorsys.rgb_to_hls(r/255,g/255,b/255)
print('rgb', (r,g,b))
print('hsl', (round(h*360), round(s*100), round(l*100)))
print('hex', rgb_to_hex(r,g,b))
PY

Lighten / darken (adjust HSL lightness)

python3 - <<'PY'
import colorsys
def adjust(hex_, dl):
    h=hex_.lstrip('#'); r,g,b=(int(h[i:i+2],16)/255 for i in (0,2,4))
    H,L,S=colorsys.rgb_to_hls(r,g,b); L=max(0,min(1,L+dl))
    r,g,b=colorsys.hls_to_rgb(H,L,S); return '#%02x%02x%02x'%(int(r*255),int(g*255),int(b*255))
print('lighter', adjust('#3b82f6', +0.15))
print('darker ', adjust('#3b82f6', -0.15))
PY

Contrast ratio (accessibility, WCAG)

python3 - <<'PY'
def lin(c): c/=255; return c/12.92 if c<=0.03928 else ((c+0.055)/1.055)**2.4
def lum(h): h=h.lstrip('#'); r,g,b=(int(h[i:i+2],16) for i in (0,2,4)); return 0.2126*lin(r)+0.7152*lin(g)+0.0722*lin(b)
def ratio(a,b): L1,L2=sorted([lum(a),lum(b)],reverse=True); return (L1+0.05)/(L2+0.05)
r=ratio('#ffffff','#3b82f6'); print(f'contrast {r:.2f}:1', '(AA body needs >=4.5)')
PY

Guidance

• Palettes: complementary = +180° hue; analogous = ±30°; triadic = ±120°.
• For body text, aim for contrast ≥ 4.5:1 (AA); ≥ 3:1 for large text.
• Always state colors as hex in the answer so they're copy-pasteable.