Is it possible that a print of one size has slightly different colors than another?

There are three factors that influence accurate color reproduction during printing:

1. Type of emulsion on photographic paper
2. Fluctuation (random variation) of chemicals in the lab
3. Laser linearization

Type of emulsion on photographic paper
Emulsion is the top layer of photographic paper that is responsible for receiving light on the paper and reacts with chemical reagents to finally develop (expose) the photo or photo album page. Emulsions are applied to rolls in production batches, so a batch from one order may have a different emulsion number (type) than that of another order.

Fluctuation of chemicals
For prints to be developed (exposed), the photographic paper must react with photographic chemicals. During lab operations, acceptable and tolerable chemical fluctuations can occur, which are mitigated to some extent by calibration tests conducted after each paper change (i.e., laser linearization). However, it should be noted that these fluctuations cannot be continuously monitored, so a deviation of around 5% is perfectly acceptable.

Considering the above, it can be assumed that a slight difference in prints made even a day apart is possible but acceptable.

It's also important to ensure monitor calibration.
For assistance, contact Vitavision.
Adam Jędrysik can help you solve color issues.