He wants to call other employees to pray but he is hesitant

We ask Allaah to increase you in faith and piety and to help
you to adhere to that which He has enjoined. 

You should not hesitate to advise your colleagues and remind
them about the prayer, rather that is what Allaah has enjoined. Allaah says
(interpretation of the meaning): 

“Let there arise out
of you a group of people inviting to all that is good (Islam), enjoining
Al-Ma‘roof (i.e. Islamic Monotheism and all that Islam orders one to do) and
forbidding Al-Munkar (polytheism and disbelief and all that Islam has
forbidden). And it is they who are the successful”

[Aal ‘Imraan 3:104]

“O my son!
Aqim-is-Salaah (perform As-Salaah), enjoin (on people) Al-Ma‘roof  (Islamic
Monotheism and all that is good), and forbid (people) from Al-Munkar (i.e.
disbelief in the Oneness of Allaah, polytheism of all kinds and all that is
evil and bad), and bear with patience whatever befalls you. Verily, these
are some of the important commandments (ordered by Allaah with no
exemption)”

[Luqmaan 31:17]

And the Prophet (peace and blessings of Allaah be upon
him) said: “Whoever among you sees an evil action, let him change it with
his hand (by taking action); if he cannot, then with his tongue (by speaking
out); if he cannot then with his heart (by hating it and feeling that it is
wrong), and that is the weakest of faith.” Narrated by Muslim, 49. 

Not praying is a great evil, indeed it is kufr that puts one
beyond the pale of Islam, according to the more correct of the two scholarly
opinions, because the Prophet (peace and blessings of Allaah be upon
him) said: “Between a man and kufr and shirk there stands his giving up
prayer.” Narrated by Muslim, 82. 

And he (peace and blessings of Allaah be upon him) said:
“The covenant that stands between us and them is prayer, whoever gives it up
is a kaafir.” Narrated by al-Tirmidhi, 2621; al-Nasaa’i, 463; Ibn Maajah,
1079. 

You should not even entertain the notion of not praying,
rather you should hate that thought as you would hate to be thrown into the
fire, as the Prophet (peace and blessings of Allaah be upon him) said:
“There are three things, whoever attains them has found the sweetness of
faith: when Allaah and His Messenger are dearer to him than anything else;
when he loves a person and only loves him for the sake of Allaah; and when
he would hate to go back to kufr as he would hate to be thrown into the
fire.” Narrated by al-Bukhaari, 49; Muslim, 60. 

With regard to the excuse that your colleague gives about his
clothes becoming impure, the answer is that he can clean the bathrooms
without his clothes becoming impure, and he can also set aside pure clothes
for praying in.  You should note that one who truly respects the prayer and
understands its importance and the seriousness of not praying would not give
such an excuse. 

It is essential to advise this man and others, and explain
the ruling concerning one who does not pray, and the obligation to offer
prayer on time, and that it is haraam to delay it until after work or before
going to bed, because Allaah says (interpretation of the meaning): 

“Then, there has succeeded them a posterity who have given
up As-Salaah (the prayers) [i.e. made their Salaah (prayers) to be lost,
either by not offering them or by not offering them perfectly or by not
offering them in their proper fixed times] and have followed lusts. So they
will be thrown in Hell”

[Maryam 19:59]

Ibn Mas’ood said concerning al-ghayy
(translated above as “Hell”): This is a valley in Hell which is very deep
and has a foul taste. 

And Allaah says (interpretation of the meaning): 

“So woe unto those performers of Salaah (prayers)
(hypocrites),

5. Those who delay their Salaah (prayer from their stated
fixed times)”

[al-Maa’oon 107:4-5]

Delaying prayer until its time is over is a
major sin, and not praying at all is major kufr – we seek refuge with Allaah
from that. 

And Allaah knows best. 

See also question no.
47425.