Start with your draw_pinwheel() function
During each iteration of the loop decide which color to set the turtle to using the color() function
On even iterations, use color1
On odd iterations, use color2
Use an if/else statement to do the decision making
After deciding the color, surround a call to draw_triangle() with begin_fill() and end_fill() so that drawing the triangle creates a colored triangle.
If you have have forgotten, you can use an if/else to check for even/oddness in python as follows.
my_number = 3
if(my_number % 2 == 0): # the remainder of dividing by 2 is 0
print("The number is "+str(my_number))
print("The number is EVEN")
else: # the remainder must be 1
print("The number is "+str(my_number))
print("The number is ODD")
Good luck <3