Hi,
Is there a set particular color that is used for transparency or is it a preference made by the developer? Somewhere I read that “hot pink” is what most artists use cause it’s very unlikely to actually be used in the image itself but, I can’t find that article anymore.
Bright green and magenta are two popular choices. Though these days everyone uses proper alpha channels as nobody really uses palettes any more.
Do you happen to know the rgb codes for those 2 colors? I tried to use proper transparency already but, unfortunately it turns parts of the image I don’t want to make transparent fully transparent.
I wonder if the issue is perhaps in how you are using the colors in your images. Can you describe a bit more about what you are doing? What properties pertaining to color and transparency are you setting? Is this something that occurs when you overlap two images that otherwise work?
Coming up with a nice lime green or bright pink that will be noticeable if it “leaks” into the graphic shouldn’t be the issue. You can pick them from a palette or color tool and observe the RBG channel values. Then include an alpha-channel value of 0. (RGBA with A = 0). In truth, any color with the alpha-channel set to 0 should behave properly and not adversely affect other colors.
Here is the original image which i used an online png tool to make transparent.
The result was the eyes and wings also turned transparent. So i used bright green around the areas I wanted to turn transparent and it worked. This is what i ended up with.
And… there you go 
job done