Minecraft SelectedItem: help with block data tags? [duplicate]

Basically, I need to make a testifier commands that checks for players to hold Blue or Red wool in the hand. To do this I've tried the following:

/testfor @a[team=Blue] {SelectedItem:{id:minecraft:wool}}

(it says that the UUID is in invalid format, but the team specification is not necessary so I removed it)

/testfor @a {SelectedItem:{id:minecraft:wool}

(It seems it only works with white wool)

/testfor @a {SelectedItem:{id:minecraft:wool 14}

Still not working and

/testfor @a {SelectedItem:{id:minecraft:wool,Data:14}}

But still not recognizing it as red wool... I just can't understand how and where I put the block variation Data...