Solid Colors

Difficulty Level: ⭐ Beginner Time to Complete: 15-20 minutes Prerequisites: Core Concepts, First Example

You'll Learn:

How to fill your entire LED strip with a single solid color
The difference between RGB and HSV color spaces and when to use each
How to use FastLED's efficient fill functions instead of manual loops
How to fill specific sections of your LED strip with different colors
Named color constants for readable, maintainable code

Solid colors are the foundation of LED control. This pattern demonstrates how to fill your LED strip with a single color using FastLED's efficient fill functions.

Basic Usage

Fill Entire Strip

Fill all LEDs with a single color:

cpp

// Fill entire strip
fill_solid(leds, NUM_LEDS, CRGB::Blue);

Fill a Range

Fill a specific section of your strip:

cpp

// Fill range
fill_solid(&leds[10], 20, CRGB::Green);  // LEDs 10-29

This fills 20 LEDs starting from index 10, effectively controlling LEDs 10 through 29.

Fill with HSV

Use HSV color space for more intuitive color selection:

cpp

// Fill with HSV
fill_solid(leds, NUM_LEDS, CHSV(160, 255, 255));

Understanding Color Spaces

RGB Colors

RGB (Red, Green, Blue) uses three channels from 0-255:

cpp

CRGB color = CRGB(255, 0, 0);      // Red
CRGB color = CRGB(0, 255, 0);      // Green
CRGB color = CRGB(0, 0, 255);      // Blue
CRGB color = CRGB(255, 255, 255);  // White

HSV Colors

HSV (Hue, Saturation, Value) is often more intuitive:

cpp

CHSV hsv = CHSV(0, 255, 255);      // Red
CHSV hsv = CHSV(96, 255, 255);     // Green
CHSV hsv = CHSV(160, 255, 255);    // Blue

// Convert HSV to RGB (automatic)
leds[0] = hsv;

Why use HSV?

Easier to create smooth color transitions (just increment hue)
Natural for rainbow effects
Intuitive control of brightness without changing color

Named Colors

FastLED provides convenient named colors:

cpp

leds[0] = CRGB::Red;
leds[1] = CRGB::Green;
leds[2] = CRGB::Blue;
leds[3] = CRGB::White;
leds[4] = CRGB::Yellow;
leds[5] = CRGB::Purple;
leds[6] = CRGB::Cyan;
leds[7] = CRGB::Black;  // Off

Complete Example

cpp

#include <FastLED.h>

#define LED_PIN     5
#define NUM_LEDS    60
#define LED_TYPE    WS2812B
#define COLOR_ORDER GRB

CRGB leds[NUM_LEDS];

void setup() {
    FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
    FastLED.setBrightness(50);
}

void loop() {
    // Cycle through different solid colors
    fill_solid(leds, NUM_LEDS, CRGB::Red);
    FastLED.show();
    delay(1000);

    fill_solid(leds, NUM_LEDS, CRGB::Green);
    FastLED.show();
    delay(1000);

    fill_solid(leds, NUM_LEDS, CRGB::Blue);
    FastLED.show();
    delay(1000);

    // Fill different sections
    fill_solid(&leds[0], 20, CRGB::Red);
    fill_solid(&leds[20], 20, CRGB::Green);
    fill_solid(&leds[40], 20, CRGB::Blue);
    FastLED.show();
    delay(1000);
}

Tips

Use fill_solid() instead of manual loops for better performance
HSV color space makes it easier to create smooth color transitions
Use FastLED.clear() as a shortcut for filling with black (off)
Named colors like CRGB::Red are more readable than CRGB(255, 0, 0)

Next Steps

Once you're comfortable with solid colors, move on to Animations to learn how to create dynamic effects.