As Steve said, a Sharpie can take care of most logos.
I also highly recommend the use of the throat guard. I used to think that the extension on the mask was enough until a pitched ball bounced in front of the catcher, came up, and caught me just left of my adams apple several years ago. It took me few minutes to recover from that one. Have worn the throat guard ever since.
Now the "funny" part of the story....My partner that day was an umpire who had a side business selling officials equipment. After I was hit and in obvious discomfort, he comes running in from his position as BU and says....
"Hey, Andy......wanna buy a throat protector????"