Improve serial plotter graph colors

[cousteaulecommandant]

I've noticed that the multi-plot feature of the serial plotter has too few colors; it starts cycling after 4 colors. (Also I personally don't quite like the current colors.)
This patch increases the number of colors to 8 and uses a brighter, more saturated palette so that the colors are easy to distinguish even by people with reduced color perception (blue, red, green, amber, purple, gray, aqua, black).

I made this palette a while back for plots used on technical reports because I didn't like the default one on Excel/Gnumeric, and I think it looks rather nice for line plots. I thought it could be useful for Arduino too.

Example with 4 colors:

Example with 8 colors:

Code used to generate the example (in case you want to try this):

static byte randomize(byte &data, byte factor) {
  data += (random(256) - data) / factor;
  return data;
}

void setup() {
  Serial.begin(115200);
}

#define PLOTS 8
#define FACTOR 16
static byte plots[PLOTS] = {0};
void loop() {
  for (int i=0; i<PLOTS; i++) {
    Serial.print(randomize(plots[i], FACTOR));
    Serial.print(",");
  }
  Serial.println();
  delay(10);
}