Getting dragons out of metallic x dragon is easier than regular x dragon crosses. But you will have to work on getting full dragons.
And what did you mean by "I noticed that color combo works a bit differently on them. Yellow for example is physically brought out easier compared to regular colors. " I am unsure what you meant by this.
Notice when you breed irid to yellow (regular scale/color) you wont get a nice irid -yellow combination. You might get yellow with irid smudges on it, but that's it. When working with dragons, such crosses might give you a rainbow of yellow and irid or MG like coloring. Yellow also easily appears in combination with other dragon colors too - copper, red, etc.