We used to get girls' skates dyed; it worked fine. However, polish won't work - it will just rub off, and it won't cover. Find yourself someone who does shoe repairs, and ask them to dye them. Generally, the skates need to be "baked" to set the colour, so, be careful if the skates are heatmoulded. It may not be easy to find, however - it took us some time. It's also a bit expensive if it is done right - we paid around $65 a pair, and that's a long time ago.
We tried the skate tape idea - it didn't work well- it's too shiny, and it peels off, and it looks odd (the strips going around - and we won't discuss how hard it is to manage with the lace holes.
We had our son's skates custom-made with natural soles; they look great. However, if the soles are sealed, it's hard to paint them and it will rub off.
Boys skates cost a bit more than girls, but not a lot; there is a wide range of them out there, easy to get these days (I wish it was that easy back in the day) - Jacksons make a decent assortment, Riedell an even wider range ... why not just go for the boy model instead of trying to dye white ones?
BTW: Jackson Competitor is gone, but, the next level up that replaces it (sort of/kind of) is available in black. However, I'd go a level or two below Freestyle for a beginner ... particularly if it's a lightweight/young kid ... or look at Riedell, who has a wider selection. Haven't been impressed with the quality of the boy's GAMS that I've seen, but, never looked at them too closely.