Can I mix hair dyes?

[Ohisitjustme]

I decided to dye my hair. I bought a box dye - let's say L'Oreal #4 medium brown. Thought about it and figured I'd need a second box - long hair so I went back to the shop. All gone 🙈. But there were boxes of Clairol #4 medium brown.
Can I use a mix - either one on the roots and the other on the length/or mix them up in one big bowl. Or is that a bad idea ?

I wouldnt personally.
But best to mix it all together.
That said the developer / colour ratios may be different.
Ie. 1 parts dye to 2 parts developer for 1 brand...