Socks for (a) 15 year old boy (b) 5 year old boy HELP needed with (a) style and (b) size

[CrepeDeChineWag]

I'm buying socks for a 15 year old boy I've never met (not as disturbing as it sounds, new blended family/Christmas etc) but no idea what style/colour to buy. What's a safe bet and what's a definite no no in the sock department?
Would also like to buy for 5 year old boy, style no problem but what size? Again what's a safe bet, think he is average height and average build.

Tia

My 15 year old only wears sports socks and takes size 9-12, if that's any help.

My 6 year old loves socks with characters on them - lego ninjago, star wars, superheros. Size 8-12

Thank you that is a help. White or black sports socks and which might power house? Adidas or Nike? I get the feeling you're either one or the other in the teenage world?? Maybe not. Teenage fashion, it's a mine field.

Mighty!

Plain sports socks doesn't sound v festive!

Go to Next, New Look or H&M & find some with Star Wars characters on or something.

Yes but what 15 year old boy wears novelty socks?? I've seen some fab shark socks for the 5 year old on the John Lewis website but think a bit small (4-7 which I think is shoe size rather than age)

Ds would wear them in any colour.
Maybe try a non sports brand like Superdry.

ahh Superdry, didn't think of that. Good idea.

My 15 year old only wears Nike sports socks in black or white, these www.decathlon.co.uk/sport-crew-basic-racket-sports-socks-x-3-black-id_8150415.html?iv_=iv_p_1_g_25792508576_c_93735728816_w_pla-163023036296_n_g_d_m_v__l__t__r_1o1x_pla_y_15177021_f_online_o_1251188_z_GB_i_en_j_163023036296_s__e__h_9045614_ii__vi&gclid=CP-9uZTkhdACFYcW0wodIBUP9A they are pretty hardwearing, he has size 8-11

They will be done on shoe size so I'd find out what size they wear as it varies greatly between children. Ds likes his days of the week socks