docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)

W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더). - Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외) - Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체) - Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속) 각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-23 19:21:18 +09:00
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+---
+id: css-rgb-colors
+title: "CSS RGB Colors"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["RGB", "rgb()", "RGBA", "rgba()", "RGB color model", "CSS RGB values"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.89
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["css", "web", "frontend", "w3schools", "color", "rgb", "rgba"]
+raw_sources: ["https://www.w3schools.com/css/css_colors_rgb.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[CSS RGB Colors]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+An RGB color value is defined with `rgb(red, green, blue)`, where each light source ranges from 0 to 255, and `rgba()` adds an alpha channel (0.0–1.0) to control opacity. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **RGB = Red, Green, Blue** — colors are formed by combining these three light sources. [S1]
+- **Syntax** — `rgb(red, green, blue)`. [S1]
+- **Range** — each parameter (red, green, blue) defines the intensity of the color from 0 to 255. [S1]
+- **How it mixes** — `rgb(255, 0, 0)` is displayed as red, because red is set to its highest value (255) and the others are set to 0. [S1]
+- **Black and white** — black is `rgb(0, 0, 0)`; white is `rgb(255, 255, 255)`. [S1]
+- **RGBA** — RGBA extends RGB with an alpha channel for opacity: `rgba(red, green, blue, alpha)`, where alpha ranges from 0.0 (fully transparent) to 1.0 (not transparent). [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Equal channels = gray** — setting red, green, and blue to the same value produces a shade of gray. [S1]
+- **Max one channel** — pushing a single channel to 255 while keeping the others at 0 produces a pure primary color (e.g. red, blue). [S1]
+- **Opacity via alpha** — append an alpha value with `rgba()` to make the same color progressively more transparent. [S1]
+
+## 📖 세부 내용 (Details)
+**RGB Value**
+RGB colors represent Red, Green, and Blue light sources. The syntax is `rgb(red, green, blue)`, where each parameter (red, green, and blue) defines the intensity of the color from 0 to 255. `rgb(255, 0, 0)` is displayed as red, because red is set to its highest value (255) and the others are set to 0. [S1]
+
+Examples of RGB color values shown on the page: [S1]
+```css
+rgb(255, 0, 0)    /* red */
+rgb(0, 0, 255)    /* blue */
+rgb(60, 179, 113) /* medium sea green */
+rgb(238, 130, 238)/* violet */
+rgb(255, 165, 0)  /* orange */
+rgb(106, 90, 205) /* slate blue */
+```
+
+Black is `rgb(0, 0, 0)` and white is `rgb(255, 255, 255)`. [S1]
+
+**Shades of Gray**
+Shades of gray are often defined using equal values for all three light sources: [S1]
+```css
+rgb(60, 60, 60)
+rgb(90, 90, 90)
+rgb(120, 120, 120)
+rgb(180, 180, 180)
+rgb(210, 210, 210)
+rgb(240, 240, 240)
+```
+
+**RGBA Value**
+RGBA color values are an extension of RGB color values with an alpha channel, which specifies the opacity for a color. An RGBA color value is specified with `rgba(red, green, blue, alpha)`. The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (not transparent at all). [S1]
+
+The page demonstrates the same color at increasing opacity: [S1]
+```css
+rgba(255, 99, 71, 0)    /* fully transparent */
+rgba(255, 99, 71, 0.2)
+rgba(255, 99, 71, 0.4)
+rgba(255, 99, 71, 0.6)
+rgba(255, 99, 71, 0.8)
+rgba(255, 99, 71, 1.0)  /* not transparent */
+```
+
+## 🛠️ 적용 사례 (Applied in summary)
+The color values above are the page's own demonstration examples. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+RGB function (language: CSS):
+```css
+selector {
+  color: rgb(red, green, blue); /* each 0–255 */
+}
+```
+RGBA function with opacity:
+```css
+selector {
+  color: rgba(red, green, blue, alpha); /* alpha 0.0–1.0 */
+}
+```
+
+## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
+- **RGB vs RGBA** — use `rgb()` for an opaque color defined by red/green/blue intensities; use `rgba()` when the color also needs an opacity (alpha) value from 0.0 (fully transparent) to 1.0 (not transparent). [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source.
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.89
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[CSS Tutorial]]
+- **관련 개념:** [[CSS HEX]], [[CSS HSL]], [[CSS Colors]], [[CSS Background Color]]
+- **참조 맥락:** Referenced whenever a color must be defined numerically by light intensity, or whenever an opacity channel is needed via RGBA.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — CSS RGB Colors — https://www.w3schools.com/css/css_colors_rgb.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "CSS RGB Colors" page (Astra wiki-curation, P-Reinforce v3.1 format).