It can, if you use too much or apply it too close to the roots. The formula contains conditioning agents, silicones, plant oils and phospholipids — ingredients that are chosen to make the hair feel softer and smoother, but they are also the type of ingredients that can leave fine hair looking flat or greasy when overused.
The product is designed as a light smoothing layer, not a heavy mask. The practical way to avoid a heavy finish is to control the dose and the placement. Start with a very small amount, rub it between your palms, and apply it only from the mid-lengths down to the ends. The roots produce their own natural oils, so they rarely need a leave-in product. If your hair is fine, reduce the amount further and focus on the ends, where coloured hair tends to be driest and most porous.
If you notice that your hair looks greasy or feels coated after using it, the most likely cause is too much product or application too high up. Try halving the amount and keeping it strictly on the ends. It is also worth remembering that silicones can build up over time with frequent use; if the hair starts to feel dull or heavy despite using a small amount, a periodic wash with a clarifying shampoo can remove residue. That is general hair-care advice, not a specific claim about this serum.
For hair that is naturally fine, the serum is still usable — the key is to treat it as a finishing touch for the ends rather than an all-over product.