Unless the application has an api for doing this, and you have access to a perl-callable library to use that api, the only way I could see to do this would be to do a screen-grab and then inspect the resultant bitmap.

Your problem then would be converting between the coordinate system used within the application and the screen coordinates represented in the bitmap; and that would be distinctly non-trivial.

You might also be able to use something like Pixie to obtain the color of the pixel under the cursor, but automating that would probably be quite difficult; and you still have the coordinate convertion problem to resolve.

There is nothing wrong with cross-posting questions, but it is considered polite to inform people about that, in order to avoid the risk of work duplication at various places on the Internet.

how would you do this without perl? does the application have some sort of API you can use?

perl is my favorite language, but it's not always the right choice for a given task. There may well be a perl module available to help you with this task, but choosing another language might be best for this task. AutoHotkey Is the primary language used by gamers to automate or manipulate the game while playing it. I have never used it myself but all of the gamers in my dept love it.

How to capture screen under Win32?

Not sure if you then want to process the data raw (BMP format is very easy to read) or use libraries like https://metacpan.org/pod/Imager

Using Imager getpixel

if raw and you want to read the pixels yourself, read: The simple explanation first: http://paulbourke.net/dataformats/bmp/

Now the more complex explanation: https://en.wikipedia.org/wiki/BMP_file_format

I could not find the exact post, but I know it exists on PM, it was for BMP with pack. This should do as a start: BMP file manipulation

Just know that with AutoIt3 you can do all this with 1 command: https://www.autoitscript.com/autoit3/docs/functions/PixelGetColor.htm

use Imager;
use Imager::Screenshot 'screenshot';
use Win32::GuiTest qw(FindWindowLike GetWindowText 
    SetForegroundWindow SendKeys);
    
    START:
my $img = screenshot(); #make screenshot
$img->write(file => 'screenshot.png', type => 'png' ) || 
     print "Failed: ", $img->{ERRSTR} , "\n"; #write a new sreenshot o
+ver old one 
                                              #or send error
$img=Imager->new();                              #make new image 
 $img->read(file=>'screenshot.png',type=>'png'); #read from fresh scre
+enshot
 $color = $img->getpixel(x=>68, y=>58);          #get pixel from coord
+inate x,y
 
 $img1=Imager->new();                            #make new image
 $img1->read(file=>'orginal.png',type=>'png');   #1.read from orginal 
+pcitrue i have made
 $color1 = $img1->getpixel(x=>68, y=>58);         #2. before to compar
+e element from
 $keys = (22);                                   #3. the same coordina
+tes, so when 
                                                 #4. window is change 
+on any diferent color
                                                 #5. program show doin
+ code (else)
  
  if ($color->equals(other=>$color1)) { #if color is the same
    print "ok\n"                         #print ok, do nothing.
  }
  else {                                  #else press key 22 from $key
+s 
  SendKeys ($keys, 100)
  }
  sleep 1;                                 #sleep for one sec
  goto START;                              #go back and do compare aga
+in with new screenshot
[download]

You can improve performance by only fetching a subset of the screen with screenshot:

my $img = screenshot(left => 68, right => 69, top => 58, bottom => 59);

You're also writing the screenshot to a file, then reading the same image back in again, which is a waste.

Good idea, ill try to modify the code, thanks. If someone have a suggestions, please post it :) Thanks !