It is very difficult to obtain exact results when using bleach or "discharge" techniques. It is always darker when wet for one thing...
But the key is to have the fabric already wet when you apply it to the bleach bath, and that the bleach has been stirred into the bath instead of adding it after the fabric. Make sure it is evenly and well saturated -- that is, poke it down!
It's only going to be splotchy if you try for it, or don't thoroughly wet the fabric both before and during the treatment.
To change the tone of fabric, you can also consider tea dying colors. I do that sort of thing in the microwave, using a huge pyrex bowl I have. Again, first you make the tea dye bath, then you add the already wet fabric into it and make sure it is well saturated. Tea can take a long time to impact a red or blue... again, hard to tell when wet what the end results will be.