W4rCry there are indeed chords that go with keys. Each letter in a key is the chord. i.e. in the key of C there is a C,D,E,F,G,A and B chord. The thing is that not all chords sound good. The chords are numbered from 1-7 (C=1, D=2 and so on). In Blues the chords that always sound good and are used the most often are the 1(C), the 4(F), and the 5 (G). This is simplifies because there are also 7th chords used a lot in Blues and so on but this is the general idea. Wayne suggests Griffs theory course and I can recommend it as well. As a new player when I started with BBG I found that I started to ask questions about theory. To be honest the answers from those trying to help me were like Greek.
I knew that 1) You do not need to know much theory to learn to play the Blues, and 2) I needed to know how these things worked. I was honestly not sure about the Theory course as I thought it would be over my head. I can tell you that the course is fun and the way Griff lays it out it is easy to learn. I can also say the the course has given me enough theory (I am not a master like others on the forum) that I can figure things out for myself much of the time because of the course. It is also important that you use the theory or you forget it and in my case I have done the course from beginning to end 3 times and each time I get more knowledgeable and more confident in my practice and playing. I hope this is the answer you were looking for.