Okay, nammi, let's try this:
1) Using iFile, go to the folder on your iPad following this address -
/System/Library/PrivateFrameworks/ChatKit.framework/. Inside that folder should be three PNG images:
Balloon_1.png (which is a green text bubble ... outgoing text)
Balloon_2.png (which is a gray text bubble ... incoming text) <---- this is the one you say is that odd blue...
Balloon_Blue.png (which is a blue text bubble ... outgoing iMessage text)
Are those images there? And, are they the correct color? If yes,
2) Again using iFile, go to all the themes you have installed in Winterboard. The main iFile address for themes is /var/stash/Themes... Look within each theme for this folder
[ThemeName].theme/Bundles/ChatKit.framework/. See if any have modified that particular PNG image you have as blue.
NOTE: I may have the specific folder name wrong for the themed images. I don't have Winterboard on my iPad1 any longer - so I'm going off of memory (and looking at my iPhone). You may just need to search inside every folder within every theme for that PNG image. So, you might have to look in these folders too: Bundles or com.apple.chatkit. Sorry...
Now, if you have no success there (the images are correct and no theme is changing that PNG image), the only thing I can suggest you do is build yourself a theme to make that PNG the proper gray. Cause, honestly, I have no idea why it isn't!
Especially since you've said you've done a reset, respring and a reboot!
So, if you are willing, I can help you put together a personal theme to put that PNG image back to gray. All you'll need is a personal computer (cause it's much easier than doing it on the iPad), the free program iFunbox (for Windows ... cause I hope you have a Windows PC) and the Cydia tweak OpenSSH installed. If you're willing, and have all that - let me know and we'll do some theming.
Sorry this is so complicated, but you're problem sure has me stumped...
Marilyn