I was wondering how I would go about making some flashing text for a game-over screen that reads "press z to try again". I tried using modulo however when I attempted this it would display the text for one frame and then show (about) 30 empty frames.

Any help on a simple and effective method would be greatly appreciated.

You can use something like this to achieve this effect:

blink_timer=0
blink_flag=false

function _draw()
  cls()
  if (blink_flag) print "hello"
  if (blink_timer % 30 == 0) blink_flag=not blink_flag
  blink_timer+=1
end

or some binary magic:

if (band(frame,32)!=0) print "hello"
frame+=1

will blink ~ every second @60hz (use 16 @30fps)

Here's my super simplistic method for random flashing color text....

PRINT ("GAME OVER",50,50,RND(16))

But I have been wondering how to get text to flash back and forth between 2 colors, like red and blue... for example.

BAND is a powerful command I must admit. I need to explore it at some point. However, I tend to use MOD for my timing works.

cls() n=0
circfill(0,0,90,5) -- show overlay effect
repeat
  color(0)
  if (n%16<8) color(7)
  print("g a m e",48,60)
  print("o v e r",48,68)
  color(n*8)
  print("press z to try again",24,76)
  flip()
  n+=1
until btn(4)

Tiny additional point that actually resetting the counter avoids weirdness at the integer overflow boundary:

n = (n + 1) % 10
color(n == 0 and 1 or 7)

Technically this is also avoided if your frame count is a power of 2, but so far I've found I want more control than that. Resetting also means maintaining a separate counter per effect, which may or may not meet your needs.

Good point, DDDaaannn. It is possible to let my demo run undisturbed for 18-minutes, yeah, after that it will likely mess up.