I sent the question to a few people and they sent it to a few others, here is what one of them said:
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There is no evidence of these prophecies supposedly made by Guru Tegh Bahadur in the pre-British period. They do not appear in any historical records.
The story goes that Guru Tegh Bahadur apparently looked out to the West when he was to be executed and said that soon his light skinned devotees would come and that they would overthrow the Mughals.
This just one of several attempts by the British to undermine the Panth and create a religious basis for their rule.
They were probably spread in the 1860's as a way to legalize British rule, but most importantly to increase recruitment into the British army.
They were pretty successful at first. Remember that Sikhs started to enter into the British army VERY early on. We must also remember that significant parts of Punjab were pro-British and anti-Sarkar Khalsa (Sikh kingdom). The Patiala rajas were openly allied with the British and they controlled almost all the territory South of the Sutlej.
So, this is an impossible question to answer. There wasn't anytime where all Sikhs thought of the British as good nor a time when all thought they were bad. The Panthic minded Sikhs and those who were invested in the return of Khalsa Raj were always anti-British. That's why the 2nd Anglo Sikh wars broke out with leaders like Baba Maharaj Singh and Sardar Sham Singh Attari. The Nihang Singhs were particularly anti-British and they were virtually eliminated, with the Patiala rajas even giving out hunting licences after the British takeover to go out into the jungles of Malwa and hunt Nihangs like animals.
So, there remained a group of Sikhs who were anti-British, but the establishment Sikhs quickly compromised themselves and became loyal subjects of the British crown.
That's why you have people like SIR Sundar Singh Majithia who came from a prominent Sardar family that was a supporter of Ranjit Singh but then became British subjects and were given knighthoods and other titles (Sardar Bahadur being an especially prestigious one).
What's interesting is that reform movements that arose within the panth would quickly become political in nature due to the inherent sovereignty of the Khalsa. We see this with the Namdharis, who arose primarily as a reform movement by Baba Ram Singh against excesses in regards to weddings (if he were around today!!) and the consumption of meat and the opening of slaughter houses around Punjab (remember that the Namdharis killed butchers and went a little crazy on the vegetarian thing... I know you love that Japnaam).
later, when the Singh Sabha Lehar was first starting, we should remember that it was compromised Sikh sardars that were the patrons of the movement at the beginning. they wanted this to be a purely religious revivalism, but, it quickly became more political as the intellectuals of the movement (professor Gurmukh Singh, Giani Gian Singh, etc) realized that it was impossible to separate political from religious. beginning with caste, women and idol worship issues, then morphing into attacks on the mahants controlling Gurdwaras, and then becoming a general anti-British movement.
the progress was slow. we also have to remember that the idea of ONE unified panth, while a nice fairy tale, is pretty inaccurate. these were "Sikhs" in charge of Gurdwaras. people who looked like Sikhs. but they were solidly pro-British. there were some turning points, but large scale dissatisfaction with the British, and a mass movement, as opposed to one led by a few reformers, really only began after the Rikab Ganj Morcha situation (the one that Randhir Singh went to jail for) and then only really with the start of the Gurdwara reform movement and the creation of the SGPC in 1919 and 1920 did anti-British sentiment come to a head.
but remember that there were still plenty pro-British elements, especially many of the old sampardas and deras who feared the reformers. the Akalis were taking over these historical Gurdwaras that were the main source of revenue for all these groups, and they were terrified of losing their cash cows. also large businessmen and landowners were also pro-British as they didn't want anything that compromised their business interests. what scale of the Sikh population supported the anti-British cause? who knows. but it did become a pretty impressive movement in the pre-WW 2 days, when huge morchas would go out against the British. but this was probably still a small proportion of the total Punjabi Sikh population.
By the time WW 2 was over, and it was clear the British had to leave, then all the old guys that had been supporting the British jumped on board. they knew that it would look stupid and bad to still be pro-British. and so, you have the situation that the real dedicated independence fighters were shut out of power after "independence" and the same ruling class that ran things before held onto their power after independence, which we all know was really just a transfer of power from British elites to brahmin ones.
anyways, that's a quick version of the story, we could go into a lot more detail, but I don't have the books on me at work.
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥