That's the only way you're going to be able to get rid of it. Also, brighten the gray used a little as the gray is 120, 120, 120 when it should be 128, 128, 128. Upon doing so, the A5 logo would be otherwise gone for good. For best results, build a panel around the gray. The reason why I used that gray color is it's the only color (within a very narrow range) that can fully get rid of that logo. It's there, but due to being transparent, and knowing the formula to calculate colors of varying degrees of transparency, that's going to be your only option. All you can do is build a panel around it and just make sure you don't have any text or other objects above where the logo is. Look at your BMP image once and zoom in to that gray spot. You'll still see the logo, but notice how it's so well hidden? Just making that gray surrouding it slightly lighter should fix it and make it 100% invisible (due to zero contrast). Because I didn't get the white color, this reduced my accuracy, but as you can see, it's extremely close to vanished.

When displaying graphics on the web, use PNG if you don't want any colors altered (GIF if there are 256 or fewer colors.