I'm not extremely familiar with Arduino development so I might be a bit off but some things I noticed:

1. color1, color2, color2are not very descriptive names. If they corresponds to color channels they should be named accordingly likered, green, blue`.

2. You have a couple of methods which take a time like delay_time or gap_time. It might be an absolutely ingrained standard in Arduino development that times are always measured in milliseconds but appending the unit to the name like display_time_ms or gap_time_ms would make it clear to reader what the time unit should be.

3. I'm not sure why you copy the random word you select into a buffer and then append it to a String object. It looks to me that this is an unnecessary temporary copy. If I read the documentation right this:

output = text + buffer;

essentially gets transformed into

    output = text.concat(String(buffer))

(given that text and output are String object while buffer is a char[])

So to me this looks like it could be simplified to:

    int rand = random(0,13);
    char* random_word = (char*)pgm_read_word(&(string_table[rand]));
    String text = "Your personalised reading: ";
    String output = text + random_word;

which eliminates the requirement for the temporary buffer copy.

I'm not extremely familiar with Arduino development so I might be a bit off but some things I noticed:

1. color1, color2, color2 are not very descriptive names. If they corresponds to color channels they should be named accordingly like red, green, blue.

2. You have a couple of methods which take a time like delay_time or gap_time. It might be an absolutely ingrained standard in Arduino development that times are always measured in milliseconds but appending the unit to the name like display_time_ms or gap_time_ms would make it clear to reader what the time unit should be.

3. I'm not sure why you copy the random word you select into a buffer and then append it to a String object. It looks to me that this is an unnecessary temporary copy. If I read the documentation right this:

output = text + buffer;

essentially gets transformed into

    output = text.concat(String(buffer))

(given that text and output are String object while buffer is a char[])

So to me this looks like it could be simplified to:

    int rand = random(0,13);
    char* random_word = (char*)pgm_read_word(&(string_table[rand]));
    String text = "Your personalised reading: ";
    String output = text + random_word;

which eliminates the requirement for the temporary buffer copy.