The current Acid Magic colours are green & purple, which are two very odd colour choices.
Most real-life acids are colourless, however another colour you might see is orange or yellow.
Now, transparent would be considered too powerful as a colour for a magic, and yellow would just be joked about, so orange would be a rather good addition.
tbh we do need more magic variations. We’re not on track to get any new magics until 2028 at this rate, yet vetex teasing us by adding lost and ancient magic content through dragons and bosses, the least he could do is to give us something fresh to play with through new variations.