@Holly Oakes I think that most brands generally work, the important thing is knowing how they work inside out. Thats not to say 'stick to what you know' and don't try different things, but just think about the training aspect of things. I mostly use L'Oreal day to day in the salon, and I know it would take me a long time to re-train to the same level if we converted all our colours to wella for example.
Having said that I do think it is good to try out other brands.
For prelighteners, my favourites are Wella Blondor Soft Blonde for on scalp lightening because it it gentle on the scalp and doesn't dry. For a powder lightener Blondor Powder is also nice, for a stronder powder I'd use L'Oreal Multitechniques. I use the other lighteners L'Oreal Freehand techniques for soft balayage and Platinium for strong balayage.
Toners I really like Redken Shades EQ gloss. It's a really nice acidic toner, day to day I use L'Oreal Dialight which I think is pretty good.
Permanent colour I use INOA too and I like the effect it has on the hair. Wella Koleston perfect leaves the hair really shiny and is a nice product to work with.The Wella high lift shades are great too.
Day to day I use Diarichesse as a demi, I like Wella Colour Touch too, they have some different tones than L'Oreal.
Direct dyes wise I like Joico Color Intensity for Vivid tones.
I'd start by trying different products one thing at a time. For the most basic colours you can generally get them with any brand, but in each line you will have your favourites.
