Multiple leds on one arduino pin? - LEDs and Multiplexing - Arduino Forum
For dimming multiple LEDs at the same time, which one is better, using a PWM circuit with a 555 timer (right), or just using a potentiometer (left). Both are valid and work
Arduino Lights Dimmer for Multiple Lamps
How to Control LEDs on the Arduino - Circuit Basics
Arduino Potentiometer with Multiple LEDs [Tutorial] - The Robotics Back-End