As much as I don't like how broad and strange this question is, I will venture an answer.

TL;DR:

You can't in most cases. Not by color.

Here are some things to keep in mind:

• Cooking method can make color vary widely. Take chicken or pork, for instance; cooking it in liquid will make its color like the liquid, frying will make it brown-ish, grilling will make it charred, and smoking will make it red-ish or brown-ish, depending on what wood you use.

• Marinades and seasoning will tend to color the meat as it absorbs the seasoning. The longer it marinates, the bigger color difference. That color usually carries over into the cooked meat.

• Different cuts of meat color differently. Compare for example ground beef vs. steak vs. check roast.

Here are some ways you can tell meat doneness reliably:

For thicker cuts of meat, like a pork loin roast, chicken, turkey, etc. the best method is to use a meat thermometer. They are inexpensive and you can find digital and analog models in many grocery stores in the kitchen utility section. Here is a guide to help with safe cooking temperatures.

For thinner cuts of meat, like steak, pork chop, hamburger, boneless chicken breast, etc. there are a few easy ways:

• Make a small cut in the thickest part of the meat, and apply a little pressure onto the meat and look at the color of the juices. For white/pink meats, the liquid should be clear when it is done. Pink/red liquid indicates it is not well done yet. Red meats are a little different, red liquid indicates rarer meat, and brown liquid indicates more doneness. This is the only way you can use color to check doneness.

• Press the meat slightly with your finger and use this handy little trick to check doneness using your hands. I recommend using a plastic/rubber glove when you touch the meat, for food safety and mitigate the chances of a burn to your finger.

tl;dr: You don't.

Here are a few of the problems with trying to judge doneness based solely on color:

1. Depending on the size and shape of the meat, the exterior color may or may not be any sort of indication of the internal temperature, which is the important part. A large, squarish roast cooked at a high temperature might be beautifully browned on the outside and totally raw inside.

2. A collary to this is that in order to judge interior color, you must cut into your meat. If done with insufficient resting, this can result in all your lovely juices escaping and leaving you with several pounds of leathery awful. If you haven't quite hit your desired doneness, then you've now changed how the meat will cook by cutting in.

3. The desired color will differ depending on the type of meat. A pink beef steak is excellent. A pink chicken breast is a no-no.

4. Starting color can vary between even the same cut of meat from different producers. There are some local producers here that produce lovely blood-red steaks, and others that look rather sickly and dark pinkish at best (I buy the former). Different starting conditions means different ending conditions even though they might be equally done.

5. Color is difficult to judge reliably under different conditions. What looks lovely and medium-rare in your brightly florescent-lit kitchen might appear rather different in my dimmer, incandescent-lit one. Or maybe you've got a big window and medium-rare looks different at high noon than it does at midnight (midnight steaks are the best, you guys).

Instead, get an instant-read thermometer and use temperature to determine doneness. This is an indispensable kitchen tool. You can wing it without one, but there is no better way to accurately and reliably determine doneness. Here is an answer I quite like that discusses this in relation to roasts, but the last few paragraphs about temperature are applicable to other meats as well.

Yes, I know that professional chefs (especially those at steakhouses and the like) can and will deliver perfectly-cooked steaks without checking temperature. However, those guys are utilizing years of experience with their cuts, their equipment, and many more senses than sight alone. They poke the steaks to examine how the muscle fibers have contracted; they have an intuitive sense for timing built up from thousands of previous attempts. Not all chefs can do this anyway, and they get away with it only because speed and efficiency are as much a concern as accuracy. (Quite frankly, most diners don't know what medium-rare looks like.) You are probably not these guys, and you can do better than they do anyway. Use a thermometer, don't go by color.

if you are cooking a steak on a grill and the grill is the right temperature you can usually tell by how it looks and how it bleeds.

• Rare - Marked/browned on all sides
• Medium-rare - starting to bleed and marked/browned on all sides
• Medium - Bleeding red and Marked/browned on all sides
• Medium-Well - starting to bleed clear to only bleeding clear
• Well Done - is well done
• Burnt - this takes a while at the right temperature

I know this from more than 10 Years of grilling all kinds of meats.