I sautéed chicken gizzards for quite a while, then added water and boiled another 15 minutes but they are still pink inside. Are they safe to eat even though they are pink inside?
After boiling for that period of time (especially after sauteing), the gizzards have certainly reached a "safe" temperature. They are probably not really good eating though. Gizzards are a tough piece of meat. They benefit from a low and slow cooking process. Here's a pretty good article from Livestrong. Among other advice, they suggest braising (or boiling) first for 15 or so minutes, then searing at a very high heat.
Here's a pretty typical recipe for Southern Fried Chicken Gizzards. It starts with simmering the gizzards for 45 minutes or longer, then cooling, then breading.
Safety really isn't the issue here, or color; after 15 minutes of boiling, you have well surpassed the USDA recommended temperature of 165F (74C). For good flavor though, they need more time.
Traditionally, chicken or turkey giblets are cooked by simmering in water for use in flavoring soups, gravies or poultry stuffing. Once cooked, the liver will become crumbly and the heart and gizzard will soften and become easy to chop. Cooked giblets should have a firm texture. Casseroles containing giblets should be cooked to 165 °F. Stuffing should also be cooked to 165 °F. Chicken giblets are commonly fried or broiled. Leftovers should be refrigerated within 2 hours.