Hi the end of my cat 5 cable is frayed so I have borrowed the crimper from work, the cables are coloured orange, blue, green, brown, there are also a number of white cables.

My question it is obvious where the coloured cables go but do the white cables need to go in a certain order, or can any white cable go with any coloured cable?

Apologies for the most boring post ever.

straight through, so make a note of what they are in the other end when viewed with the plug in the same orientation, and splay them out the same way round on the unfinished end

It can be a bit fiddly getting them lined up correctly but it is doable. I used to make our CAT5 cables to custom length where I used to work

None will be white, they'll have a stripe that corresponds to one or other of the colours. They're Twisted Pairs, but splay them out as J_D says for recrimping.

i used to know them off by heart but it was a long time ago.
pin 1 is the furthest left looking at the contacts and the clip at the rear.

Yep your right none were white anyway done it now and not as fiddley as i thought. thanks guys

Unhelpfully there's absolutely no advice as to whether you use A or B. I, unfortunately, forgot what I was using halfway through doing our house but the router seemed to work it out without too much trouble.

TIA 568B is the correct way to connnect Cat5/6, but as long as you wire them the same each end so that the cores go straight through it doesn't really matter.

Easiest way to remember is 568B, 'B' being for British, 568A, 'A' being for America.

If you connected one end as an A and one as a B you will have made a crossover cable.

Also 100Mb Ethernet only uses two pairs out of the four in Cat5.

Sparky and Qualified data cabling engineer 😉