Thank you very much for your reply.  It was actually mustard algae and not coming off with my brush.  After wrapping a cloth around the brush and working really hard on the brushing…it did come off and has been treated.  I am interested to know what products you recommend for yellow algae, as I anticipate this may happen again.

What I did this time was, brushed entire pool (as 50% was golden and not moving with regular brushing)

1. 5 bags of Lite Shock
2. 1 full bottle of Bioguard Algae 600 (a bottle was added 2 days prior as well when brushing had not lifted)
3. 1 clarifier soc in skimmer
4. Next morning vacuumed pool on waste immediately followed by re brushing entire pool.
5. That evening, rebrushed entire pool again, and added 2 jugs of liquid chloring and 3 more bags of lite shock.
6. Repeated waste vacuum in morning.
7. Waiting now to see how we do over next few days and what settles.

Any advice is welcome. My pool is about 35,000 litres full deep end.