Thanks Guys! I commend you on the Rules comments.
1. There's Tricksters out there who do not follow the Color standard. So you could match the colors up and still have a Problem!
2. The "Big Box" store Stat's are Junk. It might say Honewell but it's not the same quality thermostat a Professional will install.
3. Wiring the New 'Stat incorrectly will cost you MONEY. I had one last year where an Electrical Engineer was Sure he could do it. Hummm... Yes, the Magic Smoke Came Out Of The Transformer. I also had one last Fall where the HO (Home Owner) installed it and it worked in the Cooling mode but as soon as he turned it to Heat.... Yes, you guessed it.
4. If you check the Contractors map here, you'll hopefully find a Professional to give you a hand. You might possibly have a 'stat that won't work with your system.