T-Mobile and CEO John Legere have launched an all-out assault on the mobile wireless industry in the past year, with its industry-shaking "Uncarrier" initiatives and competitive pricing, but for Legere, AT&T has always been a special target. So Legere is probably pleased that T-Mobile has won a court decision prohibiting an AT&T subsidiary from using its color scheme.

A federal court ruled in favor of T-Mobile granting the insurgent wireless carrier a preliminary injunction against AT&T's subsidiary Aio Wireless because Aio's plum color scheme infringes on T-Mobile's trademark magenta. The judge, Lee Rosenthal, wrote in his decision that the plum of Aio Wireless in its advertisements, logo, and other marketing materials was "confusingly similar" to T-Mobile's magenta color on its logo. Aio uses plum in its logo, ads, and store design.

Rather than just another way for T-Mobile to needle AT&T in any way possible, the confusion caused by AT&T's subsidiary's choice of primary color and font may be legitimate. Aio Wireless, like T-Mobile, is a no-contract carrier offering low-cost wireless plans -- likely to the same market segment as T-Mobile. After the Aio Wireless service launched last year, T-Mobile filed a lawsuit against the company immediately, according to the Verge.

In the suit, T-Mobile said that Aio Wireless's color scheme, mixed with Aio's similar wireless services, and was confusing customers into thinking that the AT&T subsidiary was actually associated with T-Mobile.

According to the Verge, winning a preliminary injunction requires presenting a case strong enough that it has a high probability of winning in the final decision. Part of what T-Mobile said in its suit was that AT&T's acquisition and introduction of Aio Wireless was clearly done to "compete directly with T-Mobile," which the judge agreed with, saying, "the record is clear that Aio wanted to capture T-Mobile customers," according to court documents. Another damning part of the opinion mentions that a company hired by AT&T to do focus group testing on Aio Wireless commercials sent a report specifically saying that, "because the plum color was so similar to T-Mobile magenta, focus-group members were initially confused into thinking that the commercials were affiliated with T-Mobile," according to the court opinion.

With the final decision still yet to be winded up, with monetary damages yet to be decided, the probability that T-Mobile was being infringed upon by Aio Wireless caused the court to decide to lay the injunction against Aio's use of the plum color. The decision leaves open the possibility of using a different shade of plum, so we may not see the end of T-Mobile/Aio grudge match yet.

Responding to its preliminary victory over AT&T and its T-Mobile-looking subsidiary (aka the Evil Empire and its clone army), T-Mobile said in a statement:

"A federal court has halted AT&T's transparent effort to infringe on T-Mobile's distinctive magenta trademark. T-Mobile [U.S. Inc.] is very pleased that the federal court in Texas has ordered Aio Wireless, a subsidiary of AT&T, to stop infringing T-Mobile's magenta trademark. The court agreed with us that Aio can't continue infringing T-Mobile's magenta mark by using large blocks of what it has called "plum," and told Aio to stop using magenta or similar colors in all of its marketing and advertising, including stores, web sites and social media. The Court's ruling, coming after extensive argument and a three-day hearing, validates T-Mobile's position that wireless customers identify T-Mobile with magenta and that T-Mobile's use of magenta is protected by trademark law."