First, your block must be on the -None- layer, otherwise, it will make everything the color of the layer it is on.
Edit your block. Pick all elements and use the color button to change their color.
Or better yet...
Create a layer for each color.
Edit your block and put all the objects on the appropriate layer.
From your description I guess you are looking to change the colour in the part environment (as you mentioned Editing the Sketch)/ I have just checked 2012 vs 2014 and actually cannot see a difference- that is I do not get the "Sketch Color" option on the right click menu of a block- I only get this in both versions when right clicking the sketch that contains the block. Therefore the way I have found to change the colour is to preselect the block and then use the menu Edit > Appearance > Sketch/Curve Color- hope the image below clarifies this.
Funny, I assumed he was talking about a drawing block not a part block.