There's a Steven Moffat mystery layered into Doctor Who Series 8 that has me puzzled. I'm not talking about the Missy story-arc, I have my theories on that, one involves Clara, the other which I'm leaning more towards involves a female regeneration of the Master - Master-Mistress-Missy - with "Heaven" being her TARDIS desktop theme. No, this mystery is much more of an odd conundrum, and it began on Christmas Day 2013...In what could be considered as a throwaway line or a comment on his new kidneys the Twelfth Doctor announces "I don't like the colour". But in the same way that the phone wasn't just hanging off the hook near the end of The Time of the Doctor it is clear that Moffat was making reference to a new series 8 mystery.By the way, there are no spoilers for future episodes on Doctor Who series 8 below, just my personal speculation.So let's review our evidence.Clara's new love interest, a teacher at Coal Hill School and an ex-soldier. We've only seen a few minutes of Mr Pink on screen but from those moments it may be deduced that he is haunted by events that occurred whilst serving as a soldier, possibly he took a life or something equally as distressing. Danny is a mystery in himself, clearly he's going to play an important role this season and not just be "the boyfriend". Next Saturday's episode, Listen, promises to tell the story of a date, I'm expecting that to involve Danny and Clara and possibly reveal more of his past.Lieutenant Journey Blue of the Combined Galactic Resistance. A soldier. Our first real hint that there has to be some colour connection came when Clara was introduced to her and commented "I just met a soldier called Pink."Colonel Morgan Blue. Journey's Uncle. A soldier.We've not seen this many soldiers with coulourful names since the days of Gerry Anderson's Captain Scarlet and the Mysterons - somehow I don't think there's a connection.But wait, we're not done. He's no Captain Scarlet, but...Will Scarlet. Has a good sword hand. A member of Robin Hood's band of men, so essentially a soldier.Four 'soldiers' all with colourful names.But it doesn't stop there. In the trailer for episode 4 , Listen, we can see this...A Soldier.During Into The Dalek, Journey Blue commented to the Doctor "You don't like soldiers much, do you?", his reply "You don't need to be liked. You have all the guns." But not this green toy soldier, his gun seems to have been broken off. Either that or he's taking a sup of coffee and holding a TV remote!So why do we have colourful soldiers appearing throughout this season? What is the connection? Will Moffat go all Cluedo on us and introduce a Reverend Green or Mrs Peacock into the series? Are they somehow tied into the Missy story-arc or completely separate?It is a mystery that has me quite bamboozled. One thing I do lean towards though is that Danny Pink holds the key to it all.I'm not sure how, or indeed if, this is tied into the colour theme but let me offer a wild idea about Mr Pink which has been buzzing around my head since Saturday night, after viewing the Next Time Teaser Trailer for Listen at the end of Robot of Sherwood. You might want to check it out first...Right, here goes.Journey Blue had a brother who died in the opening moments of Into The Dalek, his name was Kai. It was quite hard to get a proper look at him as he only appeared for a couple of seconds whilst Wasp Delta was shaking around evading the Dalek attack. With such little screen time and no lines he went uncredited in the titles, but take a look at this screen grab...Is there a chance that's Sam Anderson?Could it be that our Impossible Girl has found her Impossible Boy?I turn to you, dear reader, to help me out; to offer suggestion, theory or wild speculation. Whatever you think could be the connection between the colourful soldiers or the mystery behind Danny Pink please share in the comment section below.