I think this makes more sense as her personal choice. Spectres usually work in the shadows, I don't think that they would have uniforms and coordinated color schemes.
Well, since they aren't actually working in secret and are official spokespersons for the Council, I'd give them an uniform of sorts they can wear if they want to. Honestly, after Shepard's stunt with the endorsements I wouldn't be surprised if there was Spectre merchandise. They need to pay for their gear somehow, right? 
Well I wouldn't say it's Spectre armor per se, more that it's her preferred style with the logo on it. Because Nhilus had his own, Saren has his own, and Jondum bau had his own armor
Yep, true. I'm not sure what they even need a logo for. Nihlus was wearing Phantom armor by Serrice Council, an Asari manufacturer. Jondum Bau was wearing the standard Salarian armor with different colors. Saren was wearing something from the Geth Armory winter collection which was so blatantly obvious that a simple photo of him should have been enough to convict him.

By the goddess! tehehehehe
The guy is half machine from the very beginning, he looks more like Geth than Turian. Note the blue tubes inside his chest. Just like Legion later.
Even more offtopic: Did anyone notice that in ME1 Tali's right arm is ... well... Geth?

Geth Infiltrator! Cyborg! No wonder she was so good with machines... 
On the Spectre topic: Spectres make not much sense once you think about it. They are both secret agents and public figures. Everyone knew about Saren and Shepard. Nihlus was known to the crew of the Normandy, too. They mentioned a few of his past exploits. They are outside the law and only answer to the Council, their job is to go where the Council can't act themselves... eh what? If they are officially sanctioned spokespersons for the Council, if the Council has direct oversight over the Spectres... then they are acting themselves through their agents. Who are basically just diplomats with guns. The difference between sending a fleet or a Spectre is lost on me. Both are actions by the Council, so it's clearly Citadel business. Stuff like that would only work if Spectres were unknowns... but even rent-a-cops can just check your ID and confirm you're one. Not to mention that the Council itself made Shepard's identity and promotion public to such a degree that even numbnut Conrad Verner knew about it an hour later.
Also... if you have the support of the Council (which means access to massive stores of information, connections and resources) why do you have to pay for your gear? What's the point? Do they want agents that are good merchants? Would it be asked for too much to get a proper ship (even if it's just a fighter craft) and access to Spectre level weapons and armors right from the start? Oh no, let's waste time earning money when the fate of the galaxy is at stake. So efficient.
Another point... the Spectre office only turns up in ME3. And it's not very impressive. Where were the Spectres in ME1? Why didn't they grab Shepard right after their promotion, dragged them into their offices and gave them a manual? Why didn't they throw Shep into a combat simulator to see if they are as good as they said? Why has Shepard no access to any training or intelligence hehehe during ME1?
The Council recruits special persons into the Spectres... the one thing they all have in common is that they are exceptional warriors. Almost all of them were soldiers. Which is awesome and all... but that doesn't mean they'd make good spies. While some are good at investigating crime, most Spectres are used for combat. Instead of sending an entire platoon, the Council sends a single Spectre. Who has to pay for their own gear and probably doesn't get their travel expenses refunded either. Clever. The Council is saving so much money that way. 
If Spectres only answer to the Council, then by definition they can not be part of any other organization, they can not answer to their species' government or military. I doubt Saren or Nihlus were still in line for Primarch, Jondum Bau wasn't in STG anymore (if ever) and Tela Vasir wasn't a Huntress either. Only Shepard is being a special snowflake again.
Spectres suck. They are terrible spies, the Council can't even disavow them, they have basically no support from the Council and they have to deal with all the crap jobs you can't give to the actual military.
Back to Tela Vasir's armor: The first time I saw her in the game I thought, "No way she's a real Spectre, they wouldn't run around in an uniform. She's probably an impostor who believes Spectres have a logo." ... turned out she was indeed real. Imagine James Bond walking into a casino, wearing his tuxedo... with MI6 stenciled on the back.
Did I mention a certain lack of realism and consistency in the ME franchise? It bears repeating.