Like this. Pick the resistors to get the appropriate current for each LED, making the resistors the same for each color. There thus may be 3 sets of resistors.

You can drive the transistors with PWM if you like.

^{simulate this circuit – Schematic created using CircuitLab}

Or use the WSxxx individually adressable LEDs and simply send the same brightness information to each, which is easier and more flexible.

Like this. Pick the resistors to get the appropriate current for each LED, making the resistors the same for each color. There thus may be 3 sets of resistors. See Transistor's answer for considerably more detail.

You can drive the transistors with PWM if you like.

^{simulate this circuit – Schematic created using CircuitLab}

Or use the WSxxx individually adressable LEDs and simply send the same brightness information to each, which is easier and more flexible. Using the Arduino libraries it is very fast to do that, and the PWM brightness control is done inside the driver chip.

There are even 4-LED SMT parts that contain a serially accessed driver chip, RGB and a white LED.