- He is always helpful, kind towards his colleagues.
- He is always helpful and kind towards his colleagues.
Are both sentences correct?
No, only the second sentence is correct. If you are indicating two different states of being (helpful and kind) they have to be differentiated by a conjunction (in this case, "and") to make the sentence grammatically correct.
If the first sentence were spoken, it would require the speaker to provide additional clarification to the listener to describe which adjective s/he is attempting to ascribe to the person in question. That alone makes it grammatically incorrect.
Both sentences are fine, but carry different meaning as J.R. already pointed out in the comments.
He is always helpful, kind towards his colleagues.
The first sentence describes the person primarily as helpful. This is further clarified by saying that he is “kind towards his colleagues”. So the second part actually extends the “helpfulness” described first.
He is always helpful and kind towards his colleagues.
The second sentence describes the person as “helpful and kind”, having both as not necessarily related attributes. These attributes are then both specified to apply “towards his colleagues”, so it’s actually not expressed if the person is also helpful and kind to other people.
A third sentence is possible:
He is always helpful, and kind towards his colleagues.
While this one seems very similar, the “towards his colleagues” now refers to the kindness. So the “helpful” stands alone as one attribute, and “kind towards his colleagues” is the second attribute. As in the second sentence, both are again unrelated to each other.