your object has 1 material. you could give it multiple materials if you wanted too. this image above is wrong approach. the channel painting RGB is for the mask only. the diffuse is just a full colour texture. the details are full colour textures. the mask is just a (full colour texture) that controls placement of the detail channel textures and blends all that with the primary diffuse in the shader.
Multiple materials are not supported in AC, afaik. Yes, it's correct, but diffuse can be "clean", no need for any "stripes".
Don't mind the white stripe in the diffuse. But if I wan't the color variation in the diffuse and avoid the sharp edges. Do I simply have to blend the colors in some way? Like this: