Of course you can do this. DarkBASIC is really very flexible. Just update the image you are using for the health portion of your HUD, if you want it to flash when beneath a certain health level then you could use a subroutine like this (this would also work as part of a function to display your HUD) :
changehealthcolour:
if health < 10
if healthcolour = rgb(255,0,0)
healthcolour = rgb(0,255,0)
'display health using healthcolour'
return
endif
if healthcolour = rgb(0,255,0)
healthcolour = rgb(255,0,0)
'display health using healthcolour'
return
endif
endif
return