Use an ATtiny85 with Arduino IDE

1#include <DigisparkRGB.h>
2/*
3 Digispark RGB
4 
5 This example  shows how to use soft PWM to fade 3 colors.
6 Note: This is only necessary for  PB2 (pin 2) - Blue, as Red (pin 0) and Green (pin 1) as well as pin 4 support the  standard Arduino analogWrite() function.
7 
8 This example code is in the public  domain.
9 */
10byte RED = 0;
11byte BLUE = 2;
12byte GREEN = 1;
13byte COLORS[]  = {RED, BLUE, GREEN};
14
15// the setup routine runs once when you press reset:
16void  setup()  { 
17  DigisparkRGBBegin();
18} 
19
20
21void loop ()
22{
23//direction:  up = true, down = false
24boolean dir = true;
25int i = 0;
26
27while(1)
28{
29fade(COLORS[i%3],  dir);
30i++;
31dir = !dir;
32}
33}
34void fade(byte Led, boolean dir)
35{
36int  i;
37
38//if fading up
39if (dir)
40{
41for (i = 0; i < 256; i++) 
42{
43DigisparkRGB(Led,  i);
44DigisparkRGBDelay(25);//1);
45}
46}
47else
48{
49for (i = 255; i >=  0; i--) 
50{
51DigisparkRGB(Led, i);
52DigisparkRGBDelay(25);//1);
53}
54}
55}
56
57
58