Well the short answer is 'No uniforms', the long answer is below...
Early in the Sengoku Jidai daimyo didn't really have large standing armies and the majority of the soldiers were taken from the farming population and the local samurai would have to pay for the equipment of their farmers.
Each samurai had to provide a certain number of retainers according to his personal income and therefore the armies that were gathered were a multicoloured affair.
Occasionally the bigger daimyos would pay for sashimono to equip his men to make them more recognisable on the field.
Later in the period as the war got bigger daimyos started to have standing armies and therefore had more of a uniformed state for the units but generally the garments under the armour were the wearers own, so there was still a lot of colour to be had unless the daimyo was one of the top ones.
Obviously painting them to look similar in the same unit is appealing and it's how I do mine (I generally play the later part of the period) but I am starting to make them a bit more different.
The above was for the lowly ashigaru but the same could be said for the lower class samurai. Higher class samurai strived to be seen on the field and would therefore try and look different to their compatriots from their armour to their sashimono design.
Heraldry in the Sengoku period wasn't really the same as in Europe. There were no hard and fast rules and if a son wanted to change the colours and general design of the banners then so be it.
The only thing to stay the same was the shape of the family mon but it's colours, sizes and frequency could change at a whim.
There's a whole lot more to this and it is a really interesting subject when you start getting into it.
Hope it's a help
cheers
James